When girls perform oral sex on a guy their heads bop up and down like a chicken. Refers to girls who can do the job FAST. Also refers to girls who give blowjobs to anyone.
JOE: I'll let that chicken head blow me anytime!
BOB: Pass that ugly bitch around then!
JOE: I'll hook you up guy. She'll blow anyone.
JEFF: Dude, my girlfriends a CHICKEN HEAD shes so good!
RYAN: You lucky bastard...