alert tovtr phrasal sepphrasal verb, transitive, separable: Verb with adverb(s) or preposition(s), having special meaning, divisible--for example, "call off" [=cancel], "call the game off," "call off the game."
(make aware of)
be on the alert
keep alertviintransitive verb: Verb not taking a direct object--for example, "She jokes." "He has arrived."