desusar

A rarely used verb, itself marked 'poco usado' (little used) in the RAE dictionary, meaning to stop using or practicing something. In practice, almost nobody uses the verb desusar directly — its past participle desusado (old-fashioned, obsolete, unusual) is far more common and is what most learners will actually encounter.

• Con el tiempo se desusó esa costumbre en el pueblo. — Over time, that custom fell out of use in the town.
• Es una palabra desusada que ya casi nadie emplea. — It's an old-fashioned word almost nobody uses anymore.
• El vestido tenía un corte desusado para la época. — The dress had an unusual cut for the period.

Trying to use desusar as an active, everyday verb — dejar de usar is what a modern speaker would actually say; desusar itself is nearly obsolete, ironically fitting its own meaning.