Temperamental
WordNet
adjective
(1) Likely to perform unpredictably
"Erratic winds are the bane of a sailor"
"A temperamental motor; sometimes it would start and sometimes it wouldn't"
"That beautiful but temperamental instrument the flute"- Osbert Lancaster
(2) Subject to sharply varying moods
"A temperamental opera singer"
(3) Relating to or caused by temperament
"Temperamental indifference to neatness"
"Temperamental peculiarities"
WiktionaryText
Adjective
- of, related to, or caused by temperament
- 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.