Abbott-Smith Manual Greek Lexicon
ἀγρυπνέω (G69)
4 ἀγρυπνέω , -ῶ ( ἄγρυπνος , seeking sleep ; ἀγρεύω , ὕπνος ), [in LXX chiefly for שׁקד ;] to be sleepless, wakeful (Theogn., Xen., al.); metaph. (LXX) = cl. ἐγρήγορα , to be watchful, vigilant : Mk 13:33 , Lk 21:36 , Eph 6:18 , He 13:17 .† SYN. : γρηγορέω , q.v.; νήφω , associated with γ. in I Pe 5:8 , expressing a wariness which results from self-control, a condition of moral, not merely mental alertness (v. M, Th. , I, 5:6).
G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain