The term 'losing steam' is often used to describe a situation where someone or something gradually loses momentum, energy and enthusiasm. Some possible antonyms for this term might include 'gaining ground', 'building momentum', 'energizing', 'surging forward' or 'picking up steam'. These terms all suggest a more positive and forward-moving state of affairs, where progress is being made and momentum is not being lost. Other potential antonyms could include 'steadying the ship', 'regaining momentum', 'gaining a second wind', 're-charging', or 'reviving'. All of these antonyms suggest ways to overcome the sense of stagnation or apathy implied by the term 'losing steam'.