a grin like a Cheshire cat

a very wide smile

Usage notes: The Cheshire cat is a character in Lewis Carroll's book Alice in Wonderland and is famous for its big smile.

I just presumed he'd got the job because he walked in here with a grin like a Cheshire cat.

Name	Pronounced	Usage
Jagienka	yah-GYEN-kah	Polish
StaŠA	-	Serbian, Slovene, Croatian
AscensiÓN	ah-then-SYON (Spanish), ah-sen-SYON (Latin American Spanish)	Spanish
Aleksej	-	Slovene
Ablett	['æblit]
Evridiki	-	Greek