The antonyms for the phrase "keep in reserve" are to utilize, consume, expend, use up, deplete, exhaust, drain, empty, and spend. These words imply that something is not being saved or held back but is instead being used or consumed immediately. When we use these words, we are communicating a sense of urgency or necessity, emphasizing the idea that resources are scarce and must be put to use effectively. While "keep in reserve" suggests a sense of foresight and planning, these antonyms focus on action and the here and now. So, if you're looking for ways to express the opposite of "keep in reserve," these antonyms are a great place to start.