A sexual act where a female gets into the fetal position and their partner sticks his/her thumb into the female's anus and thier middle and ring fingers into the females vagina. After the insertion is completed, the female must be lifted and brought to the nearest stairway and be rolled down the stairs, just like a bowling ball down the lane, hence the name "filthy bowler"
Person1: "Hey, you know craltan."
Person2: "Yeah, Why?"
Person1: "He gave Tammi the filthy bowler, isn't he cool?"
Person2: "Did he really? He is the coolest!!"