Chesh·ire cat, the /ˌtʃeʃə ˈkæt $ -ʃər-/
people sometimes say someone is ‘grinning like a Cheshire cat’ to mean that they have a big and rather silly smile on their face. This phrase comes from a character in Alice’s Adventures in Wonderland by Lewis Carroll, which disappears until only its big smile can be seen.

[TahlilGaran] Dictionary of Contemporary English ▲