WordReference Random House Unabridged Dictionary of American English © 2026
os1
(os),USA pronunciation n., pl. os•sa (os′ə).USA pronunciation
os2 (os),USA pronunciation n., pl. o•ra (ôr′ə, ōr′ə).USA pronunciation
os3 (ōs),USA pronunciation n., pl. o•sar (ō′sär).USA pronunciation
OS,
O/S,
o/s,
- Anatomy, Zoologya bone.
- Latin
- 1540–50
os2 (os),USA pronunciation n., pl. o•ra (ôr′ə, ōr′ə).USA pronunciation
- Anatomy, Zoologya mouth or orifice of the body.
- Latin ōs mouth
- 1730–40
os3 (ōs),USA pronunciation n., pl. o•sar (ō′sär).USA pronunciation
- Geologyan esker, esp. when of great length.
- Swedish ås (plural åsar ) ridge
OS,
- Language VarietiesOld Saxon.
- Computingoperating system.
- Chemistry[Symbol, Chem.]osmium.
O/S,
- Time, (of the calendar) Old Style.
o/s,
- Time, (of the calendar) Old Style.
- out of stock.
- Business(in banking) outstanding.
-
Latin oculus sinister - Language VarietiesOld Saxon.
- Old School.
- Old series.
- Time(of the calendar) Old Style.
- Naval TermsSee ordinary seaman.
-
Latin oculus sinister - Naval TermsSee ordinary seaman.
'o.s.' also found in these entries (note: many are not synonyms or translations):
KO
- o
- cos
- double-O
- Eötvös torsion balance
- Eötvös unit
- F.O.S.
- nos-
- O, o
- ordinary seaman
- os
- O.S.A.
- O.S.B.
- OSD
- O.S.F.
- OSS
- point-of-sale
- pos.
- tick-tack-toe
- so
- SOS