Synonyms: wide-awake, heads-up
Definition: fully alert and watchful
Usage: played heads-up ball
Similar words: alert, watchful
Definition: engaged in or accustomed to close observation
Usage: caught by a couple of alert cops; alert enough to spot the opportunity when it came; constantly alert and vigilant, like a sentinel on duty
Synonyms: wide-awake, unsleeping
Definition: fully awake
Usage: the unsleeping city; so excited she was wide-awake all night
Similar words: awake
Definition: not in a state of sleep; completely conscious
Usage: lay awake thinking about his new job; still not fully awake