Coined on League of Legends by player Doublelift when he face checked a brush with 4 enemies in it. This was on an official stream, and since then, the Riot Games creator, Phreak, has been heard to use the phrase "pulling a doublelift" to mean face checking an area by themselves with a large number of enemies in it.
Unless you can see at least 4 out of 5 enemies on the map or have all of your team mates with you, there may be an ambush so face checking is generally considered a bad course of play, using a ward or a revealing spell being a safer choice. Otherwise you will have successfully pulled a double lift, which will inevitably result in brutal virtual gang rape.
Phreak: "Haha, lets make it a definition!"
Announcer: Annie has been slain by Garen! (Assisted by Warwick, Veigar and Graves)
Randon player 1: "Ouch, gang raped!"
Random player 2: "That's what she gets for doublelifting."