A Manhattan jury got a lesson in Harlem gang slang yesterday — as an NYPD narcotics expert and a defense lawyer sparred over the meanings of words like “yak” and “scud” caught on surveillance recordings.

Testifying against five alleged leaders of the notorious 137th Street gang called “Goons on Deck,” Detective Alfred Hernandez of the NYPD Drug Enforcement Task Force told jurors that “yak” means “crack” and “scud” marijuana.

But Frank Rothman, lawyer for accused kingpin Jaquan “Jay Cash” Layne, tried to persuade jurors that “yak” actually means cognac and “scud” means, as the lawyer apologetically put it, “a female who appears to be attractive from a distance but who isn’t, close up.”

“You’ve never heard of sipping yak?” Rothman asked at one point.

“No sir,” the narcotics expert answered. “I’ve heard of somebody yacking, as in throwing up.”