Temperamental

Adjective

 * 1)  of, related to, or caused by temperament
 * 2) subject to changing and unpredictable emotional states; moody, capricious; sometimes used figuratively to describe user-unfriendly or unstable machines or software that are either complicated and/or have poorly written instructions and are subsequently difficult to operate.

Thesaurus
affective, arbitrary, atavistic, bluff, bodily, born, brusque, capricious, changeable, characteristic, coeval, congenital, connatal, connate, connatural, constitutional, crabbed, crabby, cranky, crotchety, curt, dispositional, emotional, erratic, excitable, explosive, fanciful, fantasied, fantastic, fickle, flaky, freakish, genetic, grouchy, gruff, grumpy, harebrained, hereditary, high-strung, hot-blooded, hot-tempered, hotheaded, huffish, huffy, humorsome, hypersensitive, impatient, in the blood, inborn, inbred, incarnate, inconsistent, indigenous, inherited, innate, instinctive, instinctual, intellectual, irascible, irritable, kinky, maggoty, mental, mercurial, miffy, moody, motiveless, native, native to, natural, natural to, notional, organic, oversensitive, peevish, petulant, physical, prickly, primal, quirky, sensitive, short, short-tempered, snappish, spiritual, testy, tetchy, thin-skinned, ticklish, touchy, uncertain, undependable, uneven, unpredictable, unreasonable, unreliable, unrestrained, unstable, vagarious, vagrant, variable, volatile, wanton, waspish, wayward, whimsical

Derived terms

 * temperamentally