1. to lose strength, confidence, or momentum towards the completion of something; to weaken or stumble in the final stages
The runner began to falter at the end of the marathon.
O corredor começou a vacilar no final da maratona.
2. to show signs of hesitation or uncertainty when nearing the conclusion of a task or speech
His argument started strong but began to falter at the end.
Seu argumento começou forte, mas começou a vacilar no final.