Full Definition of REGAL. 1. : of, relating to, or suitable for a king. 2. : of notable excellence or magnificence: splendid.— re·gal·i·ty \ri-ˈga-lə-tē\ noun. — re·gal·ly \ˈrē-gə-lē\ adverb. See regal defined for English-language learners.efinition of REGAL for Kids. : relating to or suitable for a king or queen: royal.