temperamental

capricious, changeable, changeful, fickle, fluctuating, fluid, freakish, impulsive, inconstant, mercurial, mutable, uncertain, unsettled, unstable, unsteady, variable, volatile, whimsicalpouty, sulkycholeric, crabby, cranky, cross, crotchety, grouchy, grumpy, irascible, irritable, peevish, petulant, quick-tempered, short-tempered, snappish, snippety, snippy, testy, waspish

equable, evenimmutable, inflexible, invariable, unalterable, unchangeablechangeless, constant, settled, stable, steady, unchanging