A — 1: ὁμοθυμαδόν
(Strong's #3661 — Adverb — homothumadon — hom-oth-oo-mad-on' )

"of one accord" (from homos, "same," thumos, "mind"), occurs eleven times, ten in the Acts, 1:14; 2:46; 4:24; 5:12; 7:57; 8:6; 12:20; 15:25; 18:12; 19:29, and the other in Romans 15:6 , where, for AV, with one mind," the RV has "with one accord," as throughout the Acts. See MIND.

Acts 2:1
B — 1: αὐθαίρετος
(Strong's #830 — Adjective — authairetos — ow-thah'ee-ret-os )

from autos, "self," and haireomai, "to choose, self-chosen, voluntary, of one's own accord," occurs in 2—Corinthians 8:3,17 , of the churches of Macedonia as to their gifts for the poor saints in Judea, and of Titus in his willingness to go and exhort the church in Corinth concerning the matter. In 2—Corinthians 8:3 the RV translates it "(gave) of their own accord," consistently with the rendering in 2—Corinthians 8:17 . See WILLING.

B — 2: αὐτόματος
(Strong's #844 — Adjective — automatos — ow-tom'-at-os )

from autos, "self," and a root ma--, signifying "desire," denotes of oneself, moved by one's own impulse. It occurs in Mark 4:28 , of the power of the earth to produce plants and fruits of itself; Acts 12:10 , of the door which opened of its own accord. See SELF. In the Sept., Leviticus 25:5 , "spontaneous produce;" Leviticus 25:11 , "produce that comes of itself;" Joshua 6:5; 2—Kings 19:29 , "(that which groweth) of itself;" Job 24:24 , of an ear of corn "(falling off) of itself (from the stalk)."

B — 3: σύμψυχος
(Strong's #4861 — Adjective — sumpsuchos — soom'-psoo-khos )

"lit., "fellow-souled or minded" (sun, "with," psuche, "the soul") occurs in Philippians 2:2 , "of one accord."