mental picture is a noun meaning "a clear and telling mental image". It carries one recorded sense.
a clear and telling mental image
“he described his mental picture of his assailant”
“he had no clear picture of himself or his world”
“the events left a permanent impression in his mind”
Definitions, synonyms and semantic relations for mental picture come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.