jack-in-the-box Get Printable Handwriting Hear It! Say It! Write It! Learn It! Spelling Test Definition noun. a toy that pops out of a box when opened. Example Sentence The baby laughed when the clown sprung out of the jack-in-the-box. More Example Sentences She laughed when the jack-in-the-box popped out. Synonyms toy; surprise; plaything Antonyms work Hear It! Say It! Write It! jack-in-the-box Switch to cursive Start Share with your friends: