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
Giampaolo	jahm-POW-lo	Italian
Dijana	dee-YAH-nah (Croatian), DEE-yah-nah (Croatian)	Croatian, Serbian, Slovene, Macedonian
Helga	['helgə]
Melton	['meltən]
Atallah	-	Arabic
Twila	TWIE-lə	English