Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† būtȳ̆rum (ȳ, Sid. Carm. 12, 7; bŭ-tyron, Aen. Mac. Herb. c. de ruta. buturum, Edict. Diocl. p. 15), i, n., = βούτυρον [said to be a Scythian word, but prob. βοῦστυρός; Engl. butter], butter, Cels. 4, 15; 4, 18; 5, 26, 30; Col. 6, 12, 5; Plin. 11, 41, 96, § 239; 28, 9, 35, § 133 sq.