The telephone equivalent of phishing. Vishing is the act of using the telephone in an attempt to scam the user into surrendering private information that will be used for identity theft. The scammer usually pretends to be a legitimate business, and fools the victim into thinking he or she will profit.
See "Defend Yourself Against Identity Theft" in Webopedia's "Did You Know...?" section.
See also "VoIPowering Your Office: Vishing, Hijacking, Bots, and Other Entertainments" on VoIPPlanet.com.