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
Oddr	-	Ancient Scandinavian
Judah	JOO-də (English)	Biblical, Jewish
Lucilla	[lu:'si:lə]
Seble	-	Eastern African, Amharic
Gaetane	-	French
Hasim	-	Arabic