Spirit; pluck. Considering it is also a vulgar term for semen, it is rarely used in its normal form due to the obviously easy possibility to misinterpret it.
"That athlete shows a lot of spunk on the soccerfield"
"What?!"
"He shows a lot of spirit and determination"
"Oh."
An acronym meaning Sports Utility Nutritional Energy Kick. A nutritional drink that despite a large marketing campaign, failed due to its confusion with the slang term spunk meaning semen.
Andre: I like drinking Spunk before i exercise Rodney: That is disgusting Andre: Not that kinda spunk!