underactive Get Printable Handwriting Hear It! Say It! Write It! Learn It! Spelling Test Definition adjective. not active enough; sluggish or slow. Example Sentence She has an underactive thyroid. More Example Sentences My underactive pet sleeps most of the time. Synonyms inactive; sluggish Antonyms active; lively Hear It! Say It! Write It! underactive Switch to cursive Start Share with your friends:
