This is the term for when a guy will take one for the team and keep the friend of the girl his friend is pursuing occupied, in order to assist his friend with getting laid. This usually involves having sex with the less attractive girl. The golden rule regarding this is to switch off from time to time, so that everyone may enjoy the fruits of the labor, and miss out on some of the bitter taste of non-preferable sexual partners.
This can be linked to the term, "I will be your Huckleberry."
"Hey John, I am going to try and fuck that girl tonight, but their friend keeps interrupting us. They said we can go back to their place.. What's that? Yea, the hambeast is her friend that I am going to ask you to pull a hucklebuck on."
"Ok, Jimmy. I will hucklebuck her. I owed you one after last weekend."