1. A plan or strategy that is so well designed that it cannot fail, even if executed by someone who lacks skill or intelligence
We came up with a foolproof plan to win the competition.
Desenvolvemos um plano à prova de erros para vencer a competição.
2. A scheme that is virtually guaranteed to succeed due to its simplicity or careful design
The foolproof plan involved saving money every month without exception.
O plano à prova de erros envolvia poupar dinheiro todos os meses sem exceção.