1.) When an object's true value is perceived as much less than the seller's asking value.
2.) Someone who participates in the act.
3.) Cleverly-concealed plagiarism, with just enough changes to get past others' legal rights.
1.) Have you seen the prices of a Mac Pro? What a rip off. I could buy two equally-powerful PCs for that much.
2.) The Great Giana Sisters is just a rip off of Super Mario Bros.