Lexical Definition

‎συνεφίστημι‎ synephístēmi (soon-ef-is'-tay-mee) to attack ^G:V
from ‎σύν‎ and ‎ἐφίστημι‎

rise up together.

• to stand up together, i.e. to resist (or assault) jointly

Abbott-Smith

* συν-εφ-ίστημι
to place over. Pass.,
1. to stand over (Thuc.).
2. to rise together: seq. κατά, c. gen. pers. (against), Ac 16:22.†

Abbott-Smith References

Liddell-Scott-Jones

συνεφίστημι-ίστημι

and συνεφίστημι-ιστάνω [Refs 2nd c.BC+]: aorist 1 -επέστησα[Refs 4th c.BC+]:—set as watchers or guards, τοὺς ἱππεῖς [Refs 1st c.BC+]: metaphorically, set on the watch, make attentive, τοὺς ἀναγινώσκοντας [Refs 2nd c.BC+]

__2 seemingly intransitive (i.e. τὸν νοῦν), attend to, observe along with, ἐπὶ τὰ λεγόμενα [Refs]; uncertain reading in [Refs 2nd c.AD+]
__II passive συνεφίστημιίστᾰμαι, with aorist 2 active, stand over, superintend along with or together, [Refs 5th c.BC+]
__II.2 rise together, κατά τινων against them, [NT]
__II.3 occur together, τινι with.. , [Refs 1st c.AD+], variant for{συνυφ-} in [Refs 3rd c.AD+]

_{LSJ Scripture Refs: Acts.16.22}