Having no cause or producing agent; self-originated; uncreated.

Without just ground, reason, or motive: as, causeless hatred; causeless fear.

Without cause.

adverb. Without cause or reason.

adjective. 1. Self-originating; uncreated.

adjective. Without just or sufficient reason; groundless.

adjective. Having no obvious cause; fortuitous or inexplicable

adjective. groundless or unreasonable

adjective. having no cause or apparent cause

adjective. having no justifying cause or reason

"If any human acts may loosely be called causeless, they are the minor acts of a healthy man; whistling as he walks; slashing the grass with a stick; kicking his heels or rubbing his hands."

unintended  unmotivated  

causelessly  

deep-seated  groundless  ill-concealed  impotent  inextinguishable  

accidental  adventitious  aimless  aleatory  casual