The Evan is a term used to describe the act of having sex with one's coat on. typically the male will aquire his jacket and proceed to boff (mate with) the female. Other phrases include the Double Evan, in which the female is also wearing a coat, or the Half-Evan in which the male has removed half the coat. The much more rare version of this, of course, is the Frozen Evan. This is when the male is wearing a fluffy down ski jacket. this often will get in the way of things and is chosen only by the most daring of Evaners.
"James and i did The Frozen Evan, you know, The Evan, only with a ski jacket, in order to spice things up in the bedroom, last night."
"Did it work?"
"Not even a little, the feathers in the down of his coat kept poking through and scratching me.