Used as a phrase. It means to sit somewhere and think about the idea you have or to shut up and think more about what you are going to say before you move on to what. Define sit: to rest on the buttocks or haunches —often used with down; perch, roost — sit in a sentence Definition of sit on in the Idioms Dictionary. sit on phrase. What does sit on expression mean? Definitions by the largest Idiom Dictionary. Product Catalog Search. Search the entire SitOnIt Seating catalog of chairs and seating solutions: task chairs, conference chairs and multipurpose chairs in mesh. Define sit on. sit on synonyms, sit on pronunciation, sit on translation, English dictionary definition of sit on. vb 1. to be a member of 2. informal to suppress 3. Task chairs manufactured by SitOnIt Seating. Your source for ergonomic office chairs, conference chairs, multipurpose chairs, stacking chairs, custom chairs, quality. Synonyms for sit on at Thesaurus.com with free online thesaurus, antonyms, and definitions. Dictionary and Word of the Day. Definition of sit on the fence in the Idioms Dictionary. sit on the fence phrase. What does sit on the fence expression mean? Definitions by the largest Idiom Dictionary. Sit on definition, to rest with the body supported by the buttocks or thighs; be seated. See more.