to give up, quit, admit defeat
A fixed reflexive phrase meaning to give up or admit defeat — literally "to give oneself as defeated." It's used across the Spanish-speaking world as the standard way to say someone has stopped trying or has conceded.
Learners sometimes drop por ("darse vencido") — the preposition is fixed and required; the phrase only works as darse por vencido.
Want to practice? Try a conjugation exercise.
"darse por vencido" means "to give up, quit, admit defeat".