STRONGS NT 69: ἀγρυπνέω

ἀγρυπνέω, (ῶ; (ἄγρυπνος eqluiv. to ἄϋπνος); to be sleepless, keep awake, watch (equivalent to γρηγορέω (see below)); (from Theognis down); tropically, to be circumspect, attentive, ready: Mark 13:33; Luke 21:36; εἰς τί, to be intent upon a thing, Ephesians 6:18; ὑπέρ τίνος, to exercise constant vigilance over something (an image drawn from shepherds), Hebrews 13:17. (Synonyms: ἀγρύπνειν, γρηγορεῖν, νήφειν: "ἀγρύπνειν may be taken to express simply ... absence of sleep, and, pointedly, the absence of it when due to nature, and thence a wakeful frame of mind as opposed to listlessness; while γρηγορεῖν (the offspring of ἐγρήγορα) represents a waking state as the effect of some arousing effort ... i. e. a more stirring image than the former. The group of synonyms is completed by νήφειν, which signifies a state untouched by any slumberous or beclouding influences, and thence, one that is guarded against advances of drowsiness or bewilderment. Thus it becomes a term for wariness (cf. νᾶφε καί μέμνασ' ἀπίστειν) against spiritual dangers and beguilements, 1 Peter 5:8, etc." Green, Critical Notes on the N. T. (note on Mark 13:33f).)