expression, godan verb (-ru)
become an expert; master something
Idiomatic expression meaning to reach a high level of proficiency in a skill or art. Often used in the form 〜に堂に入る.
彼のピアノの腕前はもう堂に入っている。
His piano skills have already reached an expert level.
彼女の料理は堂に入ったものだ
Her cooking is truly masterful.