idioms

  a dark horse (someone with a secret ability or skill) I didn’t know that Molly could paint. She is such a dark horse. I think he is the dark horse in this race.   dark horse – English Vocabulary

a cuckoo in the nest (an unwelcome person in a group) Eric always got good grades, so his unruly peers see him as a cuckoo in the nest. You don’t think I’m a cuckoo in the nest, do you?   cuckoo in the nest – English Vocabulary

  act as a guinea pig (to be the subject of a medical or other experiments) We are looking for a volunteer to act as guinea pigs for a new AIDS vaccine. Students in this school are to act as guinea pigs for the new teaching methods.   act as …

  cock and bull story (a fanciful and unbelievable story) He told me a cock and bull story about being late. Do you expect me to believe that cock-and-bull story?   cock and bull story – English Vocabulary

  catnap (a short sleep) If I could take a catnap now, I would probably feel much better later on. When you are sleepless at night, avoid taking catnaps during the day.   catnap – English Vocabulary