From Longman Dictionary of Contemporary Englishgrey matterˈgrey ˌmatter British English, gray matter American English noun [uncountable] informalINTELLIGENT your intelligence, or your brain
Examples from the Corpus
grey matter• Engineers have a good helping of functional grey matter with which to devise theories.• She wondered if she could think with what was left of her grey matter.• It just requires a little time and activity from the old grey matter.• Some of that climber's grey matter has been revived and placed into a robot-climbing machine.• While away those dark winter evenings and exercise the grey matter at the same time!• Could there be a more splendid way to get the grey matter working? 