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
Aeschylus	ES-kəl-əs (English)	Ancient Greek (Latinized)
Rosy	ROZ-ee	English
Tau	-	Southern African, Tswana, Sotho
Dagmar	DAHK-mahr (German), DAHG-mahr (Finnish)	Danish, Swedish, Norwegian, Icelandic, German, Czech, Slovak, Finnish
Pier	PYER (Italian), PEER (Dutch)	Italian, Dutch
Tancredi	-	Italian