Definition of sell:
to agree to transfer good
s or provide service
s in exchange
; (professional wrestling slang) In professional wrestling, to pretend that an opponent's blows or maneuvers are causing legitimate injury; to act
"I don't know what she was selling when she pretended she liked him."
"1922: What a sell for Lena! - Katherine Mansfield, The Doll's House (Selected Stories, Oxford World's Classics paperback 2002, 354)"