twenty one Get Printable Handwriting Hear It! Say It! Write It! Learn It! Spelling Test Definition noun. 1 the cardinal number that is the sum of twenty and one; 2 a gambling game using cards Example Sentence She is twenty one years old. Spelled as 2 words. Synonyms 21; XXI; 1 more than 20 Antonyms zero Hear It! Say It! Write It! twenty one Switch to cursive Start Share with your friends: