The phrase "put lid on" means to cover or conceal something, but there are a number of antonyms or opposite words that describe what happens when a lid is not put on something. Some examples of antonyms for "put lid on" are: reveal, expose, unveil, uncover, or unmask. When we don't put a lid on something, we let it out into the open, and thereby expose it to the world. Some synonyms for these antonyms are to disclose, display, manifest, or communicate. So, while "put lid on" means to hide or protect something, the opposite words suggest a process of opening up and revealing something.