"Feels one's oats" is an idiom that means to be energetic and overly confident, usually due to youth or success. Some synonyms for this phrase would include "on a high," "pumped up," "fired up," "in one's prime," "full of oneself," and "swaggering." These phrases all suggest an individual who is unafraid to take risks and who exudes an air of confidence and self-assuredness. It is important to note that while feeling one's oats can be a positive trait, it can also lead to arrogance and recklessness. Therefore, it is important to channel this energy and confidence in a productive and responsible way.