unit square Get Printable Handwriting Hear It! Say It! Write It! Learn It! Spelling Test Definition noun. a square with sides of one unit length. Example Sentence The unit square has sides of length 1. More Example Sentences Each side of a unit square equals one. Synonyms square of one; one square unit Antonyms rectangle; triangle Hear It! Say It! Write It! unit square Switch to cursive Start Share with your friends: