In medieval architecture,  a projecting water spout carved in the form of a human, animal or monstrous figure with an open mouth.  Gargoyles function to throw rainwater clear of the building to which they are attached. Web resource here.

Screen Shot 2018-01-02 at 9.17.21 AMGargoyles. Ely Cathedral, England.  12th century.  Photo: Dun.can.