Mousy/ˈmaʊsi/ Definition 1 of 2Pro Tip 1/3Personality Trait Use 'mousy' to describe someone's quiet and unassuming personality, not just appearance. Despite his achievements, he has a rather mousy demeanor. Pro Tip 2/3Not Negative 'Mousy' isn't inherently negative, but it doesn't imply confidence which is often valued. Her mousy nature made her well-liked by her peers. Pro Tip 3/3Often Overlooked 'Mousy' can suggest someone is easily overlooked or underestimated in groups. The mousy student in the back was actually a math genius.