(law) Initialism of proof of service. / (medicine) Initialism of peripheral oxygen saturation. / (linguistics) Initialism of part of speech. / (retail) Initialism of point of sale or point of service.

(Internet, text messaging) Initialism of parent over shoulder (i.e. observing the young user's conversation)

(slang) Poor.

plural of PO

A post office box; a lockable box hired from the postal authorities or a private company as a collection point for mail.

(Britain) Wearing a particularly stern and disapproving expression; humourless; priggish. / (Britain) Poker-faced.

Alternative spelling of kung pao

(especially Louisiana) A traditional submarine sandwich from Louisiana, typically consisting of meat or seafood, usually fried, served on a Louisiana baguette.

plural of po' boy

Abbreviation of possessive pronoun.