temperamental
adj.adj. describing someone who changes their mood or feelings very quickly, or a machine that breaks down easily. You use this for people who are moody or for things that are not reliable.
adj. prone to sudden, unpredictable changes in mood or behavior; alternatively, describing a machine or device that is unreliable or prone to failure. Often used to describe children or mechanical systems.
The old car is very temperamental and breaks down often.
The toddler was in a temperamental mood all morning, refusing to eat his breakfast or play with his toys.
While the software is powerful, it remains temperamental on older hardware, often crashing during the initial rendering phase of complex projects.
From temperament + -al.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.
Last updated May 28, 2026