A sexual act where a male clambakes his buddy's girlfriend doggy style while inserting two fingers into her anus. Then, when at time of ejaculation, male swings his poopy fingers around and into the girls mouth as she orgasms; hence the boomerang effect.
"Oh ya ol Georgie was having a great time with Ryder's swampdonkey and pulled the good old cambodian boomerang on her as she was gettin her rocks off!"
by Canadian Bear Crawl September 27, 2007