fortuitousa.[L. fortuitus; akin to forte, adv., by chance, prop. abl. of fors, fortis, chance. See Fortune.]1. Happening by chance; coming or occuring unexpectedly, or without any known cause; chance; as, the fortuitous concourse of atoms.()It was from causes seemingly fortuitous . . . that all the mighty effects of the Reformation flowed. (Robertson.)So as to throw a glancing and fortuitous light upon the whole. (Hazlitt.)2. (LAw) Happening independently of human will or means of foresight; resulting from unavoidable physical causes.(Abbott.)()()