polarized

1. When used as an adjective referring to a connector, indicates a plug that can only fit one way in a receptacle. Most often refers to a NEMA 1 two prong "Edison" plug with the neutral blade slightly wider than the hot (5/16" vs. 1/4").


http://wdgraphics.com/ebay-auctions/100_1668-WD.jpg

See WikiAnswers - If an AC reverses direction 60 Hz then why are there different-sized receptacle slots for hot and neutral since v and i are alternating direction each half cycle for more information.

2. Physics, relating to the distribution of light rays. See Classification of Polarization.