os

noun3

1. •
   An opening or entrance to a passage, particularly one at either end of the cervix, internal (to the uterus) or external (to the vagina).

   • […] monocolpate (“unisulcate”) pollen grains still have a continuous aperture membrane devoid of special openings (ora) in the exine for the emergence of the pollen tube. — 2009
2. •
   Synonym of bone.
3. •
   An osar or esker.

noun4

1. •
   (UK) An Ordnance Survey map.

   • We've got an OS of the Cuckmere area.
   • Calton Hill in Edinburgh is located at OS grid ref NT262741.
2. •
   Initialism of operating system.

   • I've decided to install two different OSes on my new laptop.
3. •
   Initialism of ordinary seaman.
4. •
   Initialism of oppidan scholar.

adjective5

1. •
   Initialism of outsize, clothes for large people.
2. •
   Initialism of oversize.
3. •
   Initialism of Old Style, a term used in English language historical studies to indicate that a date conforms to the Julian calendar instead of the modern Gregorian calendar.
4. •
   Abbreviation of offscreen, indicating a line of dialogue is spoken by someone not visible onscreen.
5. •
   Initialism of over shoulder.

adverb1

1. •
   (Australia, informal) Initialism of overseas.

   • You did the overseas trip. You went OS. — 2015