1. An explanation or reason offered that is not acceptable, legally binding, or logically sound; a pretense that fails to justify or explain something
His claim of being sick was an invalid excuse since he was seen at the mall that afternoon.
Sua alegação de estar doente era uma desculpa inválida, pois foi visto no shopping naquela tarde.
2. A justification that lacks merit, credibility, or legal standing
The student's invalid excuse for missing the deadline was rejected by the professor.
A desculpa inválida do aluno pela falta do prazo foi rejeitada pela professora.