From BiblePortal Wikipedia

Vine's Expository Dictionary of NT Words [1]

1: Φυσίωσις (Strong'S #5450 — Noun Feminine — phusiosis — foo-see'-o-sis )

denotes "a puffing up, swelling with pride" (akin to phusioo, "to puff up"),  2—Corinthians 12:20 , "swellings."

2: Ὑπέρογκος (Strong'S #5246 — Adjective — huperonkos — hoop-er'-ong-kos )

an adjective denoting "of excessive weight or size," is used metaphorically in the sense of "immoderate," especially of arrogant speech, in the neuter plural, virtually as a noun,  2—Peter 2:18;  Jude 1:16 , "great swelling words," doubtless with reference to gnostic phraseology.

Wilson's Dictionary of Bible Types [2]

 Jeremiah 12:5 (b) This is a picture of the predicament of one who is weary and disgusted with the type of Christianity that he sees around him. Since his distress in the midst of such a weak form of holiness is so great, he would be miserable indeed if he were brought into a situation where holiness abounded, godliness predominated, and the Holy Spirit is working in power. One who is made miserable by the Christians on earth would be far more miserable if he were in Heaven where the highest form of pure Christianity prevails.

 2 Corinthians 12:20 (a) No doubt this refers to the boasting of man in religious circles who are puffed up with their own importance, but who have really nothing substantial to offer. These are clouds without water, and wells that are dry.

 2 Peter 2:18 (a) The reference evidently is to the boastful language used by great religious leaders whose tongues are larger than their hands. They talk much, and do little. They boast of great things, and produce only wind. (See also  Judges 1:16).

Webster's Dictionary [3]

(1): ( n.) an unnatural prominence or protuberance; as, a scrofulous swelling.

(2): ( p. pr. & vb. n.) of Swell

(3): ( n.) The act of that which swells; as, the swelling of rivers in spring; the swelling of the breast with pride.

(4): ( n.) A protuberance; a prominence

King James Dictionary [4]

SWELL'ING, ppr. Growing or enlarging in its dimensions growing tumid inflating growing tumid inflating growing or making louder.

SWELL'ING, n. A tumor,or any morbid enlargement of the natural size as a swelling on the hand or leg.

1. Protuberance prominence.

The superficies of such plates are not even, but have many cavities and swellings.

2. A rising or enlargement by passion as the swellings of anger, grief or pride.

Easton's Bible Dictionary [5]

 Jeremiah 12:5 Zechariah 11:3

International Standard Bible Encyclopedia [6]

swel´ing  : The verb גּאה , gā'āh , means "rise up" (  Ezekiel 47:5 , etc.), so that the noun ga'ăwāh ( Psalm 46:3 ) means "arising." The "swelling" of the sea that shakes the mountains is a perfectly good translation, and "pride" (so the American Revised Version margin) is beside the mark. In  Jeremiah 12:5;  Jeremiah 49:19 parallel   Jeremiah 50:44;  Zechariah 11:3 is found the phrase ge'ōn ha - yardēn , "exaltation of the Jordan," which the King James Version translates "pride of Jordan" in Zechariah and "swelling of Jordan" in Jeremiah (the Revised Version (British and American) has "pride" throughout, with "swelling" in the margin of Jeremiah). What is described is a place, with a mass of vegetation, easily burned ( Zechariah 11:1-3 ), a lair of lions ( Jeremiah 49:19;  Zechariah 11:3 ), and a particularly dangerous place for human beings ( Jeremiah 12:5 ). The luxuriant thicket of the Jordan bank is evidently meant, which could well be spoken of as "Jordan's pride" ( OHL , "majesty of the Jordan"), and "swelling" is quite impossible.

In the New Testament "swelling" is used in  2 Corinthians 12:20 for φυσίωσις , phusı́ōsis , "puffing up," "blatant self-conceit," and  2 Peter 2:18 parallel Jude   Judges 1:16 for ὑπέρογκος , hupérogkos , "overgrown," "solemnly inane."

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [7]

( גָּאוֹן , Gaon, "excellency," "pride," etc.) OF JORDAN is a phrase occurring in the A.V. at  Jeremiah 12:5;  Jeremiah 49:19; but which should be rendered "Pride of Jordan," as in  Zechariah 11:3. It refers to the verdure and thickets along the banks, lined with willows, tamarisks, and cane, in which the lions once made their covert; but has no allusion to overwhelming billows from a rise of the waters (Reland, Palaest. p. 274). (See Jordan).