1. (a.) 1. Self-originating; uncreated.

2. (a.) Without just or sufficient reason; groundless.

3. (adv.) Without cause or reason.

accidental adventitious aimless aleatory casual chance chancy contingent designless destinal dicey driftless dysteleological fatal fatidic fluky fortuitous haphazard iffy incidental indeterminate indiscriminate inexplicable mindless promiscuous purposeless random risky stochastic stray unaccountable uncaused undetermined undirected unexpected unforeseeable unforeseen unlooked-for unmotivated unpredictable