1. to gradually lose momentum, energy, or enthusiasm for something; to become less active, intense, or effective over time
The project started with great excitement, but it began to lose steam after a few months.
O projeto começou com grande entusiasmo, mas começou a perder ímpeto após alguns meses.
2. to decline in speed, force, or intensity
The runner lost steam in the final lap of the race.
O corredor perdeu o ritmo na última volta da corrida.