Ambush Marketing

Ambush amrketing is commonly an unauthorised association by businesses of their names, brands, products or services with a sports eveent or competition through any one or more of a wide range of marketing activities. "Unauthorised" in the sense that the controller of the commercial rights in such events, usually the governing body, has neither sanctioned nor licensed the association itself or through its commercial agents.
Example-

the 1996 cricket World Cup held in the sub-continent. Though Coca-Cola was the `official' sponsor of the event, Pepsi stole the limelight with its `Nothing official about it' tagline. The instance perhaps marks the most famous example of `ambush marketing' (a marketing tactic which gained prominence globally in the Eighties) in India.