excellent supporting role; outstanding supporting actor
Used in film, theater, and television to praise a performer or character who excels in a supporting part. Can refer to the role itself or the actor.
He has appeared in many films as an outstanding supporting actor.
In this drama, the excellent supporting roles shine even more than the lead.
主役 is the lead role or protagonist, contrasting with 名脇役 which is a supporting role, albeit an excellent one.
Compound of 名 (めい, 'famous' or 'excellent') and 脇役 (わきやく, 'supporting role'). The exact historical derivation is uncertain, but the term is a straightforward combination of these elements.