noun
deuteragonist; secondary actor
In Noh theater, the actor who plays the supporting role opposite the shite (仕手). The term is domain-specific to Noh.
See also: 仕手
能では、シテに対してアドが脇役を務める。
In Noh, the ado plays a supporting role opposite the shite.
The shite is the main actor or protagonist in Noh, while the ado is the secondary actor or deuteragonist.
The exact derivation is uncertain; the term is a specialized Noh theater word.