an unpredictable or erratic action, occurrence, course, or instance

the vagaries of weather; the vagaries of the economic scene.

a whimsical, wild, or unusual idea, desire, or action.

noun

crotchet , fancy , fool notion , humor , idea , impulse , inconsistency , inconstancy , notion , quirk , whim , whimsy , bee , boutade , caprice , conceit , freak , megrim , breach , caper , daydream , digression , divergence , fantasy , kink , prank , rambling , roam , trick , waver , whimsey