IPA: /ˈdɛs.juː.tjuːd/
KK: /dɛsˈwɛtud/
A condition where something is no longer used or active.
The old factory fell into desuetude after the new one was built.
Desuetude is formed from "desuetus" (meaning unaccustomed or out of use) and the suffix "-tude" (indicating a state or condition). The word describes the state of being no longer used or the condition of disuse.
Think of something that is 'out of use' ('desuetus') to remember that 'desuetude' means a state of disuse.