The act of spreading the lips of a vagina so far that you can fit a frog in, then proceed to mash the lips together, using the blood and guts of the frog as lube.
An intimate/sexual act, available for a couple or group that includes a male. To execute a frog-smile, the male and his partner(s) would undress completely, and line up in the position for the game "leap frog," having the male as the hopper. The male would then hop over his partner(s) to drag or rub his genitals along the back area of his party member(s).
(Credit to Arin Hanson, Game Grumps).
David: She totally let me give her a frog-smile. Jeff: You're weird, stop talking to me.