- operator
- opium den
- opium joint
- opprobrious
- observation car
- ofay
- off-licence
- offenseless
- official family
- oiler
- olive drab
- ordinate
- ordnance
- organize
- ordinary
- organice
- organizer
- ortolan
- other-directed
- outcome
- outcry
- outdraw
- outdrew
- outfit
- outflank
- outlaw
- outlet
- outlier
- outman
- outpost
- outshout
- outside
- oscar
- ouster
- out
- outage
- outcrop
- outdoorsy
- outdrawn
- outface
- outguess
- overnight
- oversold
- overweight
- pad
- paddywhack
- palisade
- outsmart
- over
- overlook
- overmatch
- overpass
- overpower
- oversell
- overslaugh
- overwork
- package
- packer
- oyer
- ozone
- pacificator
- pacifier
- packing
- palimony
- pandit
- pandowdy
- panhandler
- pantaloon
- paddy
- page
- pan
- paramount
- panhandle
- pants
- papa
- par
- parcel
- pard
- parkway
- parlay
- parlor
- parlor car
- parlour-car
- parochial
- parole
- party line
- party wire
- pass
- passage
- patrolman
- pay phone
- peg
- pen
- peak
- peanut
- pelt
- pence
- penitentiary
- pennies
- pennyroyal