n. 1 in senses of WARN v. 2 anything that serves to warn; a hint or indication of difficulty, danger, etc. 3 archaic = NOTICE n. 3b. warning coloration Biol. conspicuous colouring that warns a predator etc. against attacking. warningly adv.
[ OE war(e)nung etc. (as WARN, -ING(1)) ]