desmorir

A rare, literary verb — mostly found in older or poetic texts — used reflexively (desmorirse) to mean something like to nearly die or be overcome, similar to the more common morirse de risa/amor but in a heightened, archaic register. Modern Spanish speakers essentially never use it in conversation.

• El poeta hablaba de desmorirse de amor. — The poet spoke of nearly dying of love.
• Parecía desmorirse de la risa. — He seemed to be dying of laughter.
• El personaje se desmuere de dolor en la última escena. — The character is overcome with grief in the final scene.

There's no real everyday mistake to flag — this verb is essentially extinct outside old or highly literary writing, and a learner is far better served reaching for morirse de + emotion in normal speech.