having no cause or apparent cause; "a causeless miracle"; "fortuitous encounters--strange accidents of fortune"; "we cannot regard artistic invention as uncaused and unrelated to the times"
\for-TOO-uh-tuhs; -TYOO-\, adjective: 1 Happening by chance; coming or occurring by accident, or without any known cause 2 Happening by a fortunate or lucky chance 3 Fortunate or lucky
You can describe something as fortuitous if it happens, by chance, to be very successful or pleasant. Their success is the result of a fortuitous combination of circumstances. = lucky. happening by chance, especially in a way that has a good result (fortuitus, from fors )