mixed bag is a noun meaning "a collection containing a variety of sorts of things". It carries one recorded sense.
a collection containing a variety of sorts of things
“a great assortment of cars was on display”
“he had a variety of disorders”
“a veritable smorgasbord of religions”
Definitions, synonyms and semantic relations for mixed bag come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.