forfeit
To lose something because you broke a rule or requirement.
To forfeit something means to lose it or give it up as a penalty for breaking a rule or failing to meet a requirement. When a soccer team doesn't show up for a scheduled game, they forfeit the match, and the other team automatically wins. If you forget to turn in a permission slip by the deadline, you might forfeit your spot on the field trip.
A forfeit is different from simply losing through competition. When you forfeit, you don't even get to try. The loss happens because you broke a rule, missed a deadline, or failed to meet some requirement. A chess player who runs out of time forfeits the game, even if their pieces were winning. A contestant who breaks the rules of a spelling bee might have to forfeit their chance to continue.
The word can also describe the thing you lose: “The forfeit for arriving late to the tournament was missing the first round.” In some games, players who lose must perform a silly forfeit, like singing a song or doing jumping jacks, though this playful use is gentler than the serious consequences of most forfeits.
When you forfeit something, you usually lose it through your own actions or inaction, which can make it particularly frustrating.