n. disuse, obsolescence (for example, the state of a custom that is no longer observed nor practised)
the GNU version of the Collaborative International Dictionary of English
n. The cessation of use; disuse; discontinuance of practice, custom, or fashion.
The Century Dictionary and Cyclopedia
n. Discontinuance of use, practice, custom, or fashion; disuse: as, many words in every language have fallen into desuetude.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a state of inactivity or disuse
Word Usage
"One important point that was made concerned the degree to which England has over the last one thousand years had so much to do with The Low Countries (a phrase that is now in desuetude but which I use here as neutral code for both Flanders and The Netherlands), often to the mutual commercial benefit of each party and often in ways which enriched us culturally as well as economically."