British slang meaning to hide and keep quiet, possibly deriving from the phrase let sleepingdogs lie in the sense of not making a noise or causing a disturbance. It probably originating in the 19th Century, and was used by poachers who would hide and keep quiet in order to snare rabbits or to avoid being found by gamekeepers and their dogs.
People with above average penis size who don’t recognize that 4 INCHES IS AVERAGE and more than enough to please a woman.
Michael: With your small penis, no wonder she dumped you!
Bobby: 4 Inches Is Average and more than enough to please a woman.
Michael: No way, bro! Bigger is better!
Bobby: Learn some science, Dongoloid.