grey matter

(British & Australian humorous) also gray matter (American humorous)

your intelligence It's an entertaining film but it doesn't exactly stimulate the old grey matter.

Name	Pronounced	Usage
Sanel	-	Croatian
Sachiko	sah-chee-ko	Japanese
Aragorn	-	Literature
Ernesta	-	Italian, Lithuanian
Muriel	MYUR-ee-əl (English), MUR-ee-əl (English), muy-ree-EL (French)	English, French, Irish
Tranter	TRAN-tər	English (Rare)