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
PÉTronille	-	French
RenÉE	rə-NE (French)	French, Dutch
Marjana	-	Slovene, Croatian
Norma	NAWR-mə (English)	English, Italian, Literature
Allovera	-	Ancient Germanic
Yordana	-	Bulgarian