on the alert (adjective) wakeful: alert, restless
Sinonime: aloof, away, beyond, beyond reach, distant, elusive, far, far-off, faraway, impassable, impervious, impracticable, inapproachable, insurmountable, not at hand, out of the way, out-of-the-way, remote, unachievable, unapproachable, unattainable, unavailable, unfeasible, ungettable, unobtainable, unrealizable, unworkable
Antonime: sleepy,
unaware