POS or PoS may mean:

• Point of sale. A POS device enables an efficient recording of the data that comprises a business transaction when the sale of goods or services to the customer occurs.
• EFTPOS or POS Terminal is a device by which sales transactions can be directly debited to the customer's bank account
• programmable option select , the predecessor to plug-and-play
• colloquially, piece of shit (considered vulgar)
• Part of speech, the role that a word (or sometimes a phrase) plays in a sentence.
• Parents Over Shoulder, signifying to people in chat rooms or instant message conversations that someone's parents are behind them and to watch what is said.
• Packet over SONET/SDH, a communications protocol for transferring packets over fiber networks
• P/OS, the Professional Operating System sold by Digital Equipment Corporation for their PRO-300, PRO-350, and PRO-380 PDP-11-compatible line of personal computers. (Given one of the previous definitions, one may properly wonder about the wisdom of such a name, of course.)
• Post Office Sorting van, a type of rail vehicle used in a Travelling Post Office train