Katamenō (G2650) means to remain, stay, or abide — a strengthened form of menō with the prefix kata- (down/thoroughly). It describes the deliberate, settled staying in a place rather than passing through.
Acts 1:13 records that after the Ascension, the disciples went to the upper room where 'they were staying (katanontes)' — this gathered, abiding community was the womb of Pentecost. The posture of remaining, waiting, and staying together was the context of the Spirit's outpouring. The church is not a transit station but a gathered, abiding community. The deeper menō (John 15) calls believers to abide in Christ — and katamenō captures the thoroughness of that abiding.