When the penis is soft, the dick collar is the loose skin that bunches up around the base of the head, or neck, of the penis.
Thus creating a collar-like appearance around the base of the head.
Man, I got my dick collar caught in my zipper! It hurt like a mofo!
The act of fucking someone in the ass, and upon pulling your penis out, discovering that there is a collard green wrapped around your dick.
I met this chick that was obsessed with anal. It was the only way she could get off. In fact, it went prettywell until I pulled out one time and had a collard green dick.