Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A small opening or orifice, as in a body organ or passage.
  • n. Any of the small openings or pores in a sponge.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A small opening or orifice, as in a body organ or passage.
  • n. Any of the small openings or pores in a sponge.

from the GNU version of the Collaborative International Dictionary of English

  • n. An opening; a passage.

from The Century Dictionary and Cyclopedia

  • n. An opening or entrance; a mouth; an os.
  • n. In zoology: In sponges, the opening of an incurrent canal.

Etymologies

Latin ōstium, door, opening, from ōs, mouth; see ōs- in Indo-European roots.
(American Heritage® Dictionary of the English Language, Fourth Edition)

Examples

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