From HomoExcelsior

1. A case for a blade, as of a sword. 2. Any of various similar coverings. 3. An enveloping tubular structure, such as the base of a grass leaf that surrounds the stem or the tissue that encloses a muscle or nerve fiber. 4. A close-fitting dress. 5. To encase or cover with or as if with a sheath; sheathe.

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