os 1 
(ōs)
(ōs)n. pl. o·ra (ôrə)
A mouth or an opening.
[Latin ōs, mouth; see ōs- in the Appendix of Indo-European roots.]
- pressure-cook
- pressure cooker
- pressure drag
- pressure gauge
- pressure group
- pressure point
- pressure suit
- pressure-tube anemometer
- pressurization
- pressurize
- pressurizer
- presswork
- Prester John
- presternum
- prestidigitation
- prestidigitator
- prestige
- prestigious
- prestigiously
- prestigiousness
- prestissimo
- presto
- Preston
- presumable
- presumably