Alert :: Alert (a.) Watchful; vigilant; active in vigilance.
Alert :: Alert (a.) Brisk; nimble; moving with celerity.
Alert :: Alert (n.) An alarm from a real or threatened attack; a sudden attack; also, a bugle sound to give warning..
Alertly :: Alertly (adv.) In an alert manner; nimbly.
Alertness :: Alertness (n.) The quality of being alert or on the alert; briskness; nimbleness; activity.