1. 偶然的;幸运的
You can describe something as fortuitous if it happens, by chance, to be very successful or pleasant.
1. occurring by happy chance
e.g. profits were enhanced by a fortuitous drop in the cost of raw materials
2. having no cause or apparent cause
e.g. a causeless miracle
fortuitous encounters--strange accidents of fortune
we cannot regard artistic invention as...uncaused and unrelated to the times