foamer

noun4

1. •
   A device that foams or froths liquid.
2. •
   A screw-top culinary device that comprises a pressure vessel used to hold a liquid and is charged with a compressed gas, to force the contents out of the nozzle, to create a foam.
3. •
   (slang, disapproving) A railfan, particularly an obsessive one.
4. •
   (slang, disapproving) Someone with a special interest in a particular topic, usually obsessive.