Having no obvious cause; fortuitous or inexplicable(adjective)
Groundless or unreasonable(adjective)
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Use "causeless" in a sentence
"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."
"With all this advance warning, the spectacle, two years later, of a "causeless" riot shouldn't have been surprising."
"Orat.xxix. 490, ean ten apo chronon noes archen kai anarchos ho hui& 232; s, ouk archetai gar apo chronou ho chronon despotes. (ii) In the sense of anaitios, "causeless," "originis principio carens," it is applied to the Father alone, and not to the"