n. A person who uses a wireless Internet connection without permission.
Other Forms
Many who piggyback say the practice does not feel like theft because it does not seem to take anything away from anyone. One occasional piggybacker recently compared it to "reading the newspaper over someone's shoulder."

Piggybacking, makers of wireless routers say, is increasingly an issue for people who live in densely populated areas like New York City or Chicago, or for anyone clustered in apartment buildings in which Wi-Fi radio waves, with an average range of about 200 feet, can easily bleed through walls, floors and ceilings.
—Michel Marriott, “Hey Neighbor, Stop Piggybacking on My Wireless,” The New York Times, March 05, 2006
Until now, using other people’s wi-fi was considered more cheeky than criminal. With wi-fi operating at speeds up to 20 times faster than normal connections, a piggybacker is unlikely to slow down a user’s system unless they download huge files. But there are growing concerns about the ease with which networks can be accessed. In the US last year, Brian Salcedo, 21, was sentenced to nine years in prison for siphoning credit card numbers over a wireless network from a hardware store.
—Sam Lister, “'Piggybackers' are logging into trouble,” The Times (London), August 06, 2005
2003 (earliest)
Although the genesis of warchalking arose from the Internet-inspired "free information for all" concept—with owners of short-range 802.11b or Wi-Fi standards alerting those in need of access points—the idea could take on very sinister forms if your company is warchalked and nonregistered users use your network to get on the Internet. Cell phone manufacturer Nokia has termed warchalking theft. And it's not in good stead with the FBI either, which warns that unscrupulous piggybackers cannot only slow your systems down, they could use your network to issue spam.
—Janice Brand, “Coming to a Sidewalk Near You: Warchalking,” CIO, January 01, 2003
The word piggyback — as a noun it refers to a ride on a person's back and shoulders — has had quite a ride itself through the years. According to the Oxford English Dictionary, one branch began as pick pack (the earliest use is in adverbial form from 1564), then progressed to pick back and later to pig back. Another branch went from pick a pack (1722) to pick-a-back to piggy-back (which first appeared in 1843). Curiously, the origin of these terms is unknown.