Medical Definition of Histioid
1. 1. Resembling in structure one of the tissues of the body. 2. Sometimes used with reference to the histologic structure of a neoplasm derived from and consisting of a single, relatively simple type of neoplastic tissue that closely resembles the normal, as in certain fibromas and leiomyomas. Synonym: histioid. Origin: histo-+ G. Eidos, resemblance (05 Mar 2000)