From BiblePortal Wikipedia

Vine's Expository Dictionary of OT Words [1]

A. Verb.

Gâdal ( גָּדַל , Strong'S #1431), “to become strong, grow up, be great or wealthy, evidence oneself as great (magnified), be powerful, significant, or valuable.” This verb occurs elsewhere only in Ugaritic and Arabic; it is not attested in biblical Aramaic or post-biblical Hebrew. In other Semitic languages the meaning of the word is generally represented by roots with the radicals rbh , and such a root exists in biblical Hebrew as a synonym of gâdal. These two synonyms differ, however, inasmuch as gâdal does not refer to numerical increase (except perhaps in Gen. 48:19). The Bible attests gâdal about 120 times and in every period.

This verb can signify the increasing of size and age as with the maturing process of human life: “And the child grew, and was weaned …” (Gen. 21:8). The word also depicts the “growing up” of animals (2 Sam. 12:3) and plants (Isa. 44:14) and the maturing of animal horns (Dan. 8:9) and other growing things. In the intensive stem gâdal indicates that this rearing has occurred: “… I have nourished and brought up children …” (Isa. 1:2). This stem may also imply permission: “… [He] shall let the locks of the hair of his head grow” (Num. 6:5).

Gâdal can represent the status of “being great or wealthy.” Abraham’s servant reported: “And the Lord hath blessed my master greatly; and he is become great …” (Gen. 24:35)—here the word represents the conclusion of a process. In the intensive stem the verb sets forth a fact, as when God said: “And I will make of thee a great nation, and I will bless thee, and make thy name great …” (Gen. 12:2—the first biblical occurrence of the verb).

This word is sometimes used with the meaning “to be great, to evidence oneself as great”: “And now, I beseech thee, let the power of my Lord be great, according as thou hast spoken …” (Num. 14:17). Moses is praying that God will demonstrate that He is truly great, even as He has said, and do so not by destroying His people. Such an act (destroying Israel) would make onlookers conclude that God was not able to accomplish what He had promised. If, however, He would bring Israel into Palestine, this would exhibit His greatness before the nations. This same sense appears in 2 Sam. 7:22, except with the added overtone of “magnified,” “praised as great”: “Wherefore thou art great, O Lord God: for there is none like thee, neither is there any God besides thee, according to all that we have heard with our ears.”

Another emphasis of gâdal is “to be great, powerful, important, or valuable.” This nuance arises when the word is applied to kings. Pharaoh said to Joseph: “Thou shalt be over my house, and according unto thy word shall all my people be ruled: only in the throne will I be greater [more powerful and honored] than thou” (Gen. 41:40). The Messiah “shall stand and feed in the strength of the Lord, in the majesty of the name of the Lord his God; and they shall abide: for now shall he be great unto the ends of the earth” (Mic. 5:4); He will be powerful to the ends of the earth. The nuance “to be valuable” appears in 1 Sam. 26:24 when David said to Saul: “And, behold, as thy life was much set by this day in mine eyes, so let my life be much set by in the eyes of the Lord, and let him deliver me out of all tribulation.” In this statement the second use of the verb is in the intensive stem. Perhaps the force of this could be expressed if one were to translate: “So may my life be very highly valued.…”

In the reflexive stem gâdal may signify “to magnify oneself.” God says: “Thus will I magnify myself, and sanctify myself; and I will be known in the eyes of many nations …” (Ezek. 38:23). The context shows that He will bring judgment. In this way He “magnifies Himself,” or shows Himself to be great and powerful. On the other hand, a false statement of greatness and power is an empty boast. So gâdal can mean “to boast”: “Shall the axe boast itself against him that heweth therewith? or shall the saw magnify itself against him that shaketh it?” (Isa. 10:15). In the causative stem the verb may signify “to assume great airs”: “If indeed ye will magnify yourselves against me, and plead against me my reproach …” (Job 19:5). A nuance appears in Job 7:17, where gâdal is in the intensive stem, suggesting an estimation of greatness: “What is man, that thou shouldest magnify him? and that thou shouldest set thine heart upon him?” (Ps. 8:4). When man is so insignificant, why then does God esteem him so important?

B. Nouns.

Gedûlâh ( גְּדוּלָּה , Strong'S #1420), “greatness; great dignity; great things.” This noun occurs 12 times. It means “greatness” in Ps. 71:21: “Thou shalt increase my greatness, and comfort me on every side.” Gedûlâh may refer also to “great dignity” (Esth. 6:3) and to “great things” (2 Sam. 7:21).

Gôdel ( גֹּדֶל , Strong'S #1433), “greatness.” This noun appears 13 times. Gôdel means “greatness” in terms of size (Ezek. 31:7), of divine power (Ps. 79:11), of divine dignity (Deut. 32:3), of divine majesty (Deut. 3:24), of divine mercy (Num. 14:19), or of the false greatness of one’s heart (insolence; Isa. 9:9).

Migdâl ( מִגְדָּלָה , Strong'S #4026), “strong place; wooden podium.” This noun, which occurs 49 times, usually refers to a tower or a “strong place” (Gen. 11:4-5), but it also occurs once to refer to a “wooden podium”: “And Ezra the scribe stood upon a pulpit of wood …” (Neh. 8:4).

C. Adjectives.

Gâdôl ( גָּדֹל , Strong'S #1419), “great.” The adjective gadol is the most frequently appearing word related to the verb gadal (about 525 times). Gâdôl is used of extended dimension (Gen. 1:21), of number (Gen. 12:2), of power (Deut. 4:37), of punishment (Gen. 4:13), and of value or importance (Gen. 39:9).

The verb gadal and the related adjective gâdôl may each be used to make distinctive statements. In Hebrew one may say “he is great” both by using the verb alone and by using the pronoun and the adjective gâdôl. The first sets forth a standing and existing condition—so Mal. 1:5 could be rendered: “The Lord is magnified beyond the borders of Israel.” The second construction announces newly experienced information to the recipient, as in Isa. 12:6: “… Great is the Holy One of Israel in the midst of thee.” This information was known previously, but recent divine acts have made it to be experienced anew. The emphasis is on the freshness of the experience.

Another adjective gadel means “becoming great; growing up.” This verbal adjective occurs 4 times, once in Gen. 26:13: “And the man waxed great, and went forward, and grew until he became very great.”

Vine's Expository Dictionary of NT Words [2]

1: Μεγαλύνω (Strong'S #3170 — Verb — megaluno — meg-al-oo'-no )

"to make great" (megas), is translated "to magnify" in  Luke 1:46; in  Luke 1:58 , RV, "had magnified (His mercy)," AV, "had shewed great (mercy);"  Acts 5:13;  10:46;  19:17;  2—Corinthians 10:15 , RV (AV, "we shall be enlarged"), i.e., by their faith in its practical effect he will be so assisted as to enlarge the scope of his Gospel ministry and carry its message to regions beyond them; in  Philippians 1:20 , of the "magnifying" of Christ by him in his body, i.e., in all his activities and ways. In  Matthew 23:5 , it signifies "to enlarge." See Enlarge.

 Romans 11:13Glorify.

Webster's Dictionary [3]

(1): ( v. i.) To have the power of causing objects to appear larger than they really are; to increase the apparent dimensions of objects; as, some lenses magnify but little.

(2): ( v. t.) To make great, or greater; to increase the dimensions of; to amplify; to enlarge, either in fact or in appearance; as, the microscope magnifies the object by a thousand diameters.

(3): ( v. t.) To increase the importance of; to augment the esteem or respect in which one is held.

(4): ( v. t.) To praise highly; to land; to extol.

(5): ( v. t.) To exaggerate; as, to magnify a loss or a difficulty.

(6): ( v. i.) To have effect; to be of importance or significance.

King James Dictionary [4]

Magnify, L magnifico magnus, great, and facio, to make.

1. To make great or greater to increase the apparent dimensions of a body. A convex lens magnifies the bulk of a body to the eye. 2. To make great in representation to extol to exalt in description or praise. The embassador magnified the king and queen. 3. To extol to exalt to elevate to raise in estimation.

Thee that day

Thy thunders magnified.

The Lord magnified Solomon exceedingly.  1 Chronicles 29 .

To magnify one's self, to raise in pride and pretensions.

He shall magnify in his heart.  Daniel 8

International Standard Bible Encyclopedia [5]

mag´ni - fı̄ (Hiphil of גּדל , gādhal  ; μεγαλύω , megalúnō , "to make great," "extol," "celebrate in praise"): Used especially of exaltation of the name, mercy, and other attributes of God (  Genesis 19:19;  2 Samuel 7:26;  Psalm 35:27;  Psalm 40:16;  Psalm 70:4;  Luke 1:46;  Acts 10:46 ); of God's "word" ( Psalm 138:2 ); or of Christ ( Acts 19:17;  Philippians 1:20 ). Men also can be "magnified" ( Joshua 4:14;  1 Chronicles 29:25 , etc.). In  Romans 11:13 , "magnify mine office," the word (Greek, doxázō ) is changed in the Revised Version (British and American) to "glorify."