warn

/ˈwȯrn/

Middle English warnen, going back to Old English wearnian, warnian "to be on one's guard, make aware, put on one's guard," going back to West Germanic *warnōjan- (whence Middle Dutch waernen "to provide with, give notice of a danger," Old High German warnōn), probably causative derivative of Germanic *wara- "cognizant, watchful"

verb

  1. to give notice to beforehand especially of danger or evil

  2. to give admonishing advice to : counsel

  3. to call to one's attention : inform

phrasal verb

  1. to tell (someone) to go or stay away in order to avoid danger or trouble

The neighbors warned us off their land.

verb

  1. to warn (someone) beforehand : forewarn

… in 1951, the network began to unravel, and two of its members, Donald Maclean and Guy Burgess, prewarned by fellow conspirators, jumped the night ferry to St.-Malo …