Hypakouō (ὑπακούω) is built from hypo (ὑπό, under) and akouō (ἀκούω, to hear). The literal sense is to listen-under, to hear from a subordinate position and act on what is heard. Classical Greek used it for the doorkeeper who answers the knock; the verb began with attentive responsive hearing and moved toward compliance. By the New Testament period the verb regularly meant to obey.

BDAG: to follow instructions, obey, be subject to. Louw-Nida 36.15 places it in the domain of compliance with command. The Septuagint uses hypakouō for obedience to YHWH and to commanded authority (Genesis 22:18, Exodus 24:7).

The lexicographical point that matters for Ephesians 5 is what Paul does NOT do. In Ephesians 6:1 he uses hypakouō for children: ta tekna, hypakouete tois goneusin hymōn (children, obey your parents). In 6:5 he uses hypakouō for slaves: hoi douloi, hypakouete tois kata sarka kyriois (slaves, obey your masters according to the flesh). For wives in 5:22 Paul does not use hypakouō. He uses hypotassō in the middle, governed by the mutual submission of 5:21. Paul had the obedience verb available; he chose a different verb for the wife. The translation tradition that renders the wife's verb as obey is reading hypakouō into a verse where Paul deliberately did not put it.