1
general::
1. Steal, as in They fired him when they caught him ripping off some of the merchandise. 2. Cheat, defraud, as in These advertising claims have ripped off a great many consumers. 3. Copy, plagiarize, as in He was sued for ripping off someone else's thesis. All three usages are slang from the second half of the 1900s.
American Heritage Idioms
2
general::
Phrase(s): rip something off
Inf. to steal something [from someone]. • The mugger ripped my purse off of me. • Jane ripped off a lot of money. • Somebody ripped my wallet off., Phrase(s): rip off
[for something] to tear or peel off. • My pocket ripped off, and my money is gone now! • A piece of the bumper ripped off my car., Phrase(s): rip something off (of) someone or something [and] rip something off
to tear something away from someone or something. (Of is usually retained before pronouns.) • I ripped the cover off of the book accidentally. • I ripped off the book cover., Phrase(s): rip someone off
Inf. to steal [something] from someone; to cheat someone. • That merchant ripped me off! • She rips off everyone.
McGrawhill's American Idioms And Phrasal Verbs