A ripoff (or rip-off) is a bad financial transaction. Usually it refers to an incident in which a person is overcharged for something, or receives goods or services not of the standard expected for the price. A ripoff is usually distinguished from a scam in that a scam involves wrongdoing such as fraud; a ripoff may be considered excessive, but not illegal.
In a related meaning, a ripoff is a blatant or unscrupulous copy or imitation. This is also known as a knockoff. An example is the 1988 movie Mac and Me, widely seen as a ripoff of Steven Spielberg's E.T. the Extraterrestrial. In both senses there is an associated verb "to rip off", but the location of the preposition differs between the two meanings:
In one of his standup comedy routines, Dennis Miller jokes about seeing an ad in the National Enquirer: "Learn how to avoid ripoffs - send $5."
In South Africa 'ripping off' can be making a joke of something that a person does on a regular basis; see running gag. Another related term is "ripping on" or to "rip on" something; used to describe humorous verbal abuse directed towards a person, thing or concept. Ripping on something is typically light-hearted, but can also be cruel in nature just like any type of putdown.
In musical terminology Ripping Off is a light form of plagiarism, as in 'borrowing' an established riff, phrase or idea from a musician or song. When musicians use the term among themselves they are referring to the context of 'quoting' their influences and incorporating the licks into their personal style.