Extended Strong's Greek Lexicon (Abbott-Smith based)
be watchful
Usage: ἀγρυπνέω, -ῶ (ἄγρυπνος, seeking sleep ; ἀγρεύω, ὕπνος), [in LXX chiefly for שׁקד ;] to be sleepless, wakeful (Theogn., Xen., al.); metaphorically (LXX) = cl. ἐγρήγορα, to be watchful, vigilant: Mrk.13:33, Luk.21:36, Eph.6:18, Heb.13:17.† SYN.: γρηγορέω, which see; νήφω, associated with γ. in 1Pe.5:8, expressing a wariness which results from self-control, a condition of moral, not merely mental alertness (see M, Th., I, 5:6). (AS)