a protective covering (as for a knife or sword)
"The sailor carefully slid the dagger back into its leather sheath before stowing it in his belt."
a dress suitable for formal occasions
"She wore an elegant black sheath to the gala."
A holster for a sword; a scabbard.
"The knight carefully tucked his blade back into its worn leather sheath before mounting his horse."
Alternative spelling of sheathe
"The old hunter still refers to placing his knife in its leather sheath when he finishes work."