Meaning

noun (law) a defense by an accused person purporting to show that he or she could not have committed the crime in question

noun a defense of some offensive behavior or some failure to keep a promise etc.

verb exonerate by means of an alibi

originFrom the 18th century, from Latin alibī (“elsewhere, at another place”, adverb). Probably after French alibi, which has this use since the late 14th century.

Etymology from Wiktionary, CC BY-SA 3.0