A sexual position where two men - one who's penis is thick enough to not be completely wrapped by most hands - are masturbated by someone else. To the perspective of the person who's masturbating, the thicker penis is always to their left, thus creating hand gestures spelling out "co-co" each couple of strokes made.
The inception of this sex position and it's name was inadvertently inspired by the second episode of Conan, "Murder, She Tweeted". At one point during Tom Hanks' interview segment, Tom began to make the hand gestures spelling out "co-co", leading the audience in chant. Andy Richter soon advised Mr. Hanks in jest to be careful when making the gestures, for they may insinuate something sexual. This thus in turn inspired "The Coco".
Christopher: Last night was pretty wild, huh?
Paul: Yeah! Who would've thought that the Coco would be all thanks to you and Tom? It wasn't even as awkward as I thought it'd be.
Christopher: (grins) I guess my new moniker isn't so bad after all.
Paul: Hey, At least I was on Rita's left side.