A poor or ham actor; someone whose acting is wooden, unconvincing, or inept (usually derogatory).
昨日の舞台での彼は本当に大根役者だった。
He was really a ham actor in yesterday's play.
監督は台詞を覚えられない俳優を大根役者と酷評した。
The director harshly called the actor who couldn't learn his lines a ham actor.
あの映画は名場面もあるが、主役が大根役者で台無しだ。
The movie has great scenes, but the lead's poor acting ruins it.