- happening or produced by chance; accidental: a fortuitous encounter.
- lucky; fortunate: a series of fortuitous events that advanced her career.
- happening by chance, esp by a lucky chance; unplanned; accidental
adj.1650s, from Latin fortuitus “happening by chance, casual, accidental,” from forte “by chance,” ablative of fors “chance” (related to fortuna; see fortune). It means “accidental, undesigned” not “fortunate.” Earlier in this sense was fortuit (late 14c.), from French. Related: Fortuitously; fortuitousness.