three-eighths Get Printable Handwriting Hear It! Say It! Write It! Learn It! Spelling Test Definition noun. a fraction that is equal to three parts of eight. Example Sentence Three-eighths of the class passed the test. Spelled with a hypen. More Example Sentences She used three-eighths of the total amount. Synonyms fraction; part; portion Antonyms 9 out of 10 Hear It! Say It! Write It! three-eighths Switch to cursive Start Share with your friends: