n. when a man attempts anal sex without requesting verbal permission. Often involves either precursory acts such as foreplay (rimming, anal fingering) or preceding acts (spreading of ass checks, tapping head of penis on anus, pushing the tip of the penis onto the orifice without full insertion) to signal one's attempt at anal intercourse.
After doing it doggystyle with Jackie, I started knocking on the back door. She didn't object so I totally stuck it in her butt until she screamed.
Richard Johnson kept knocking on the backdoor last night in bed, but I told him to stop since I barely know him.