1
general::
Phrase(s): slip something over on someone or something [and] slip one over on someone or something; slip something over; slip one over
to deceive someone. • Are you trying to slip something over on me? • I think he tried to slip one over on me.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Hoodwink, trick, as in Her lawyer tried to slip one over on him, but his lawyer wouldn't let him get away with it, or Don't trust Dan? he's always slipping something over on his customers. [c. 1900]
American Heritage Idioms