The top of the head; the skull.
"The surgeon carefully shaved his scalp before performing the surgery to remove the tumor from the base of his skull."
sell illegally, as on the black market
"The undercover agent was arrested after being caught trying to scalp rare stamps before they could be officially released."
To remove the scalp (part of the head from where the hair grows), by brutal act or accident.
"The fierce battle left the warrior bleeding heavily after his opponent managed to scalp him during a sudden clash."