haphazard

Random; chaotic; incomplete; not thorough, constant, or consistent.

• Do not make such haphazard changes to the settings; instead, adjust the knobs carefully, a bit at a time.

Simple chance, a random accident, luck.

• You should never talk about your own fingers, and haphazards, to genteel people. You should only talk about agreeable subjects as I do.
• I consulted my mother, who was punctiliousness itself, and decided I must go Monday, as agreed. I should be with her again on Wednesday. On such haphazards hang men's destinies sometimes.

Haphazardly.

• "[...] I suspect that it mostly happens haphazard, though afterwards various noble reasons are invented. About marriage I am cynical.”