ˌmental ˈage BrE AmE noun [countable]
a measure of someone’s ability to think, understand etc, expressed as the average age of a child with that level of ability:
a 25-year-old man with a mental age of seven
ˌmental ˈage BrE AmE noun [countable]
a measure of someone’s ability to think, understand etc, expressed as the average age of a child with that level of ability:
a 25-year-old man with a mental age of seven
Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012