The definition of fortuitous is happening by chance.(adjective)
An example of fortuitous is two people who meet during a storm evacuation and wind up marrying each other a few years later.
See fortuitous in Webster's New World College Dictionary
Origin: L fortuitus < forte, by chance < fors (gen. fortis), chance, luck < IE *bhtis < base *bher-, to bring > bear
See fortuitous in American Heritage Dictionary 4
Origin: Latin fortuītus; see bher-1 in Indo-European roots.
Learn more about fortuitous