From BiblePortal Wikipedia

Vine's Expository Dictionary of NT Words [1]

1: Συνάγω (Strong'S #4863 — Verb — sunago — soon-ag'-o )

"to assemble" (sun, "together," ago, "to bring"), is used of the "gathering together" of people or things; in  Luke 12:17,18 , "bestow," with reference to the act of "gathering" one's goods; so in  Luke 15:13 , suggesting that the Prodigal, having "gathered" all his goods together, sold them off; in  John 6:12 , of "gathering up" fragments; in  John 18:2 , "resorted," with reference to the "assembling" of Christ with His disciples in the garden of Gethsemane, there in the Passive Voice (unsuitable, however, in an English translation). In  Acts 11:26 , the RV has "were gathered together (with the church)," for AV, "assembled themselves" (possibly "they were hospitably entertained by"). The verb is not found in the most authentic mss. in  Revelation 13:10 . See Bestow , Gather , Lead , Take , No. 29.

 Mark 1:33 Luke 12:1 Matthew 23:37 Luke 13:34 Matthew 24:31 Mark 13:27Gather.

2: Συναλίζω (Strong'S #4871 — Verb — sunalizo — soon-al-id'-zo )

"to gather together, to assemble," with the suggestion of a crowded meeting (sun, "with," halizo, "to crowd, or mass:" the corresponding adjective is hales, "thronged"), is used in  Acts 1:4 . The meaning "to eat with," suggested by some, as if the word were derived from hals, "salt," is not to be accepted.

3: Συνέρχομαι (Strong'S #4905 — Verb — sunerchomai — soon-er'-khom-ahee )

"to come together" (sun, "together," erchomai, "to come"), is once rendered "assemble,"  Mark 14:53 , AV. It is frequently used of "coming together," especially of the "gathering" of a local church,  1—Corinthians 11:17,18,20,33,34;  14:23,26; it is rendered "resorted" in  Acts 16:13 , AV, where the RV adheres to the lit. rendering, "came together." See Accompany.

 Acts 15:25 Acts 13:43  Matthew 10:17 James 2:2Synagogue. 2—Thessalonians 2:1 Hebrews 10:25Gathering.

Webster's Dictionary [2]

(1): (v. t.) To collect into one place or body; to bring or call together; to convene; to congregate.

(2): (v. i.) To meet or come together, as a number of individuals; to convene; to congregate.

(3): (v. i.) To liken; to compare.

(4): (v. t.) To collect and put together the parts of; as, to assemble a bicycle, watch, gun, or other manufactured article.

King James Dictionary [3]

Assem'Ble, L simul.

To collect a number of individuals or particulars into one place, or body to bring or call togethe to convene to congregate.

ASSEM'BLE, To meet or come together to convene, as a number of individuals.