a supreme specimin of female genitalia, connoting
John: "So last night, Jane and I, y'know... for the first time. But DAMN! she had one HELL of a ninjina brah. My vision blurred and I saw stars."
Jack: "No... seriously?"
John: "Ser'sly brah. She had a ninjina dude... a nin-fucking-jina. Totally."