Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† trăgăcantha, ae, f., = τραγάκανθα, goat’s-thorn, tragacanth-bush: Astragalus tragacantha, Linn.; Plin. 13, 21, 36, § 115; 26, 14, 87, § 140; 30, 9, 23, § 78.