The Greek noun aichmalōsia (αἰχμαλωσία) denotes captivity or being taken prisoner in war — literally taken by the spear (from aichme, spear). It describes both the act of capture and the condition of being held captive.
Paul quotes Psalm 68:18 in Ephesians 4:8: When he ascended he led captivity captive. Christ defeated the powers that held humanity captive and distributed gifts to His people. The ascended Christ has taken captive sin, death, and the devil, liberating believers from bondage (Galatians 5:1). The Christian life is movement from captivity to freedom.