When you put your face between a girlsbreasts and just lay there instead a motorboat in which you make a motor sound and shake your head. When you lay, there is no time maximum or minimum so you can do it for as long as you want.
(Portmanteau word coined from "Blow job" & "Show boat.")
"Sir Elton John is nothing but an ol' blowboat!" Keith Richards hissed during his recent press conference when asked about whether the Grammy & Oscar-winning songwriter would be composing a song for the upcoming Royal Wedding.