Definition of "alert"

alert¹

/əˈlɜːt/

adjective
comparative more alert, superlative most alert
1. Attentive; awake; on guard.
2. (obsolete) brisk; nimble; moving with celerity.
  Quotations
  I saw an alert young fellow that cocked his hat upon a friend of his who entered just at the same time with myself
  1712 June 23 (Gregorian calendar), [Joseph Addison; Richard Steele et al.], “THURSDAY, June 12, 1712”, in The Spectator, number 408; republished in Alexander Chalmers, editor, The Spectator; a New Edition, […], volume V, New York, N.Y.: D[aniel] Appleton & Company, 1853
noun
plural alerts
1. An alarm.
2. A notification of higher importance than an advisory.
3. (military) A state of readiness for potential combat.
4. (computing) Synonym of bell (“bell character”).

alert²

/əˈlɜːt/

verb
third-person singular simple present alerts, present participle alerting, simple past and past participle alerted
1. To give warning to.