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
Thandiwe	-	Southern African, Xhosa
Yuli	-	Russian
Leanne	lee-AN	English
Ovidius	-	Ancient Roman
Nannie	NAN-ee	English
Klara	KLAH-rah (German, Russian, Polish)	Swedish, Norwegian, Danish, Icelandic, German, Russian, Ukrainian, Polish, Slovene, Croatian