Noah Webster's New International Dictionary of the English Language

1. (n.) An under-garment worn by the ancient Romans of both sexes. It was made with or without sleeves, reached to or below the knees, and was confined at the waist by a girdle.

2. (n.) Any similar garment worm by ancient or Oriental peoples; also, a common name for various styles of loose-fitting under-garments and over-garments worn in modern times by Europeans and others.

3. (n.) Same as Tunicle.

4. (n.) A membrane, or layer of tissue, especially when enveloping an organ or part, as the eye.

5. (n.) A natural covering; an integument; as, the tunic of a seed.

6. (n.) See Mantle, n., 3 (a).