Something that cannot be used or is not fit for using because it's broken, damaged, or inappropriate.
Combination of the prefix 'un-' (meaning not) and 'usable' (able to be used). 'Usable' comes from Old French 'user' meaning 'to use.' The 'un-' prefix negates the capability.
It's interesting that we needed a whole word for 'not usable' instead of just saying 'not good'—this shows how language creates specific words when we frequently need to describe something's broken or damaged state. Many words with 'un-' actually change meaning slightly rather than just adding 'not.'
Complete word intelligence in one call. Free tier — 50 lookups/day.