1. the period of instruction in a school; the time period when school is in session - stay after school - he didn't miss a single day of school - when the school day was done we would walk home together • Syn: school, school day • Derivationally related forms: scholastic (for: school), school (for: school) • Hypernyms: time period, period of time, period • Part Meronyms: study hall 2. the time of life when you are going to school • Syn: schooldays • Hypernyms: time of life