Fortuitous
Fortuitous , adjective
[Latin 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.
So as to throw a glancing and fortuitous light upon the whole.
2.
(LAw) Happening independently of human will or means of foresight; resulting from unavoidable physical causes. — Abbott