1. Reverse of a hard-on
2. When the sight of a disgustingly ugly piece of ass makes your dick want to curl back inwards in fear of its master whipping it out and taking it near that disgusting, ugly vajayjay.
John: Dude, I just saw pictures of Barbara Streisand and totally lost my boner. Then I looked up pictures of Cheryl Cole just to get it up again!
Dave: Yeah, I've had that. That's called a reerection!
Reserection (or res-erection), when you save an erection that had softened from unpleasant thoughts by looking at or thinking about somethingstimulating again.
My mate: Oi, did you fuck 'er last night?
Me: Fuck yeah mate, but I had to do a bit of a reserection. 'Accidentally glanced over at 'er dresser & saw a photo of her mum in a bloody wetsuit.
My mate: How'd you save it, mate?
Me: Looking next to 'er mum & looking at 'er in the wetsuit.
My mate: Fuckin' nice save, mate.