From BiblePortal Wikipedia

Vine's Expository Dictionary of NT Words [1]

1: Ποικίλος (Strong'S #4164 — Adjective — poikilos — poy-kee'-los )

"varied," is translated "manifold" in  1—Peter 1:6;  4:10;  James 1:2 , RV (AV, "divers"). See Divers , A, No. 2.

2: Πολυποίκιλος (Strong'S #4182 — Adjective — polupoikilos — pol-oo-poy'-kil-os )

"much varied" (polus, "much," and No. 1), is said of the wisdom of God, in  Ephesians 3:10 .

3: Πολλαπλασίων (Strong'S #4179 — Adverb — pollaplasion — pol-lap-las-ee'-ohn )

"many times more" (from polus, "much"), occurs in  Luke 18:30 , "manifold more," and in many ancient authorities in  Matthew 19:29 (RV, marg.; some editions in text); AV and RV text, "a hundredfold," translating hekatontaplasiona.

Webster's Dictionary [2]

(1): ( a.) Exhibited at divers times or in various ways; - used to qualify nouns in the singular number.

(2): ( n.) A copy of a writing made by the manifold process.

(3): ( n.) A cylindrical pipe fitting, having a number of lateral outlets, for connecting one pipe with several others.

(4): ( a.) Various in kind or quality; many in number; numerous; multiplied; complicated.

(5): ( v. t.) To take copies of by the process of manifold writing; as, to manifold a letter.

(6): ( n.) The third stomach of a ruminant animal.

King James Dictionary [3]

MAN'IFOLD, a. many and fold. Of divers kinds many in number numerous multiplied.

O Lord, how manifold are thy works!  Psalms 104

I know your manifold transgressions.  Amos 5

1. Exhibited or appearing at divers times or in various ways applied to words in the singular number as the manifold wisdom of God, or his manifold grace.  Ephesians 3;  1 Peter 4

International Standard Bible Encyclopedia [4]

man´i - fōld ( רב , rabh  ; ποικίλος , poikı́los ): "Manifold," which occurs only a few times, is in the Old Testament the translation of rabh , "many," "abundant" (  Nehemiah 9:19 ,  Nehemiah 9:27;  Amos 5:12 , where it is equivalent to "many"), and of rābhabh , "to multiply," "to increase" ( Psalm 104:24 , "O Yahweh, how manifold are thy works"); poikilos , properly, "many colored," "spotted," "variegated," is translated "manifold":  1 Peter 1:6 margin, "manifold temptations";   1 Peter 4:10 , "manifold grace," suggests variety , diverseness  ; polupoı́kilos has this meaning more intensely ( Ephesians 3:10 , "the manifold wisdom of God"). With this may be compared a fine passage in The Wisdom of Solomon 7:22, where it is said that in Wisdom there is "an understanding spirit, holy, one only (the Revised Version (British and American) "alone in kind," margin "Greek: sole-born"), manifold ( polumerḗs )." In like manner, pollaplası́ōn , "manifold more" ( Luke 18:30 ), indicates the varied elements of the reward of him who is faithful to Christ. In Ecclesiasticus 51:3, we have "manifold afflictions" ( pleı́ōn ).