From egeiro; to keep awake, i.e. Watch (literally or figuratively) -- be vigilant, wake, (be) watch(-ful).
see GREEK egeiro
1. properly: Matthew 24:43; Matthew 26:38, 40; Mark 13:34; Mark 14:34, 37; Luke 12:37, 39 R G L Tr text WH text As to sleep is often equivalent to to die, so once, 1 Thessalonians 5:10, γρηγορέω means to live, be alive on earth.
2. Metaphorically, to watch i. e. give strict attention to, be cautious, active: — to take heed lest through remissness and indolence some destructive calamity suddenly overtake one, Matthew 24:42; Matthew 25:13; Mark 13:35,(37); Revelation 16:15; or lest one be led to forsake Christ, Matthew 26:41; Mark 14:38; or lest one fall into sin, 1 Thessalonians 5:6; 1 Corinthians 16:13; 1 Peter 5:8; Revelation 3:2f; or be corrupted by errors, Acts 20:31; ἐν τίνι, to be watchful in, employ the most punctilious care in a thing: Colossians 4:2. (the Sept.; (Baruch 2:9; 1 Macc. 12:27; Aristotle, plant. 1, 2, p. 816b, 29, 37); Josephus, Antiquities 11, 3, 4; Achilles Tatius; others) (Synonym: see ἀγρυπνέω. Compare: διαγρηγορέω.)