When one puts their face in another person's buttocks and moves their face back and forth while making a motor boat sound with their mouth by blowing air and making their lips flap. similar to motorboating but for the rear end.
"Last night i took it to the next level with liz, i rooster tailed her and she went wild"
"take that shot and lets go out rooster tailin!"
"take that shot and lets go out rooster tailin!"
by Dr. Frankenschmingle May 21, 2009