A prolonged form of the feminine of moichos; an adulteress (literally or figuratively) -- adulteress(-ous, -y).
see GREEK moichos
a. properly: Romans 7:3; ὀφθαλμοί μεστοί μοιχαλίδος, eyes always on the watch for an adulteress, or from which adulterous desire beams forth, 2 Peter 2:14.
b. As the intimate alliance of God with the people of Israel was likened to a marriage, those who relapse into idolatry are said to commit adultery or play the harlot (Ezekiel 16:15ff; 23:43ff, etc.); hence, μοιχαλίς is figuratively equivalent to faithless to God, unclean, apostate: James 4:4 (where cf. Alford); as an adjective (cf. Matthiae, § 429, 4), γενεά ... μοιχαλίς: Matthew 12:39; Matthew 16:4; Mark 8:38. (Cf. Clement of Alexandria, strom. vi. c. 16 § 146, p. 292, 5 edition Sylb.)