Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
dis-saepĭo (less correctly dis-sēpio), psi, ptum, 4, v. a., to part off by a boundary, to separate, divide (very rare).
dissaeptum, i, n. [dissaepio], a barrier, partition: saxea domorum, Lucr. 6, 951; so too of the diaphragm: quod ventrem et cetera intestina secernit, Macr. Somn. Scip. 1, 6, § 77.