1. relating to or caused by temperament

- temperamental indifference to neatness

- temperamental peculiarities

2. subject to sharply varying moods

- a temperamental opera singer

Similar word(s): emotional, moody

3. likely to perform unpredictably

- a temperamental motor; sometimes it would start and sometimes it wouldn't

- that beautiful but temperamental instrument the flute

Similar word(s): undependable, unreliable, erratic