To surreptitiously expose an unsuspecting viewer to a picture of an anus through obfuscation. The novelty practice of rectrolling is executed through the display of digital images (typically on the World-wide Web) containing anal content when the image viewer is expecting to view an image without such content. The practice may take multiple forms, such as falsely advertising a hyperlink, or in creative photography featuring a primary non-anal subject matter that draws the viewer’s eye, resulting in some form of delay before the viewer notices the anus displayed in the photograph.
The term rectroll is a derivative of the Internet phenomenon “rickroll,” combined with an abbreviation of “rectum.”

I totally just rectrolled my boss, he’ll never have another night of peaceful sleep after he unsuspectingly saw a picture of my ass.

After reading "There is a lot of uncertainty around financial transactions and investments right now, and the wrong decision could result in dire consequences" in his daily Horrorscope, Edward climbed back into bed, pulled the sheets over his head and remained there for the rest of the day.

Edward only had enough gas in his car to get to the gas station but was not sure if he had enough money in his account to pay for gas. His cell phone service had been cut off because his payments were in arrears, and since the only way he could be sure he had enough money (to pay for gas) would be to call the bank, he felt it best to hide in bed and hope his horoscope for tomorrow was more positive.