one-eighth Get Printable Handwriting Hear It! Say It! Write It! Learn It! Spelling Test Definition noun. one part out of eight equal parts. Example Sentence Use one-eighth teaspoon of salt for the recipe. More Example Sentences She ate one-eighth of the cake. Synonyms eighth; 1/8; fractional part Antonyms seven Hear It! Say It! Write It! one-eighth Switch to cursive Start Share with your friends: