say it: sheeth
sheath is a noun meaning "a protective covering (as for a knife or sword)". It carries 3 recorded senses.
a protective covering (as for a knife or sword)
an enveloping structure or covering enclosing an animal or plant organ or part
a dress suitable for formal occasions
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for sheath come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.