a. [ F. alerte, earlier à l'erte on the watch, fr. It. all' erta on the watch, prop. (standing) on a height, where one can look around; erta a declivity, steep, erto steep, p. p. of ergere, erigere, to erect, raise, L. erigere. See Erect. ]
An alert young fellow. Addison. [ 1913 Webster ]
n. (Mil.) An alarm from a real or threatened attack; a sudden attack; also, a bugle sound to give warning. “We have had an alert.” Farrow. [ 1913 Webster ]
On the alert,
n. (Physiol.) a state of readiness to respond.
adv. In an alert manner; nimbly. [ 1913 Webster ]
n. The quality of being alert or on the alert; briskness; nimbleness; activity. [ 1913 Webster ]