un ‧ us ‧ a ‧ ble /ʌnˈjuːzəb ə l/ BrE AmE adjective
[ Word Family: noun : ↑ usage , ↑ use , ↑ disuse , ↑ misuse , ↑ reuse , ↑ usefulness ≠ ↑ uselessness , ↑ user ; adjective : ↑ reusable , used ≠ ↑ unused , ↑ disused , ↑ useful ≠ ↑ useless , ↑ usable ≠ ↑ unusable ; verb : ↑ use , ↑ misuse , ↑ reuse ; adverb : ↑ usefully ≠ ↑ uselessly ]
something that is unusable is in such a bad condition that you cannot use it