1. 
   bell mouth
   Bell-shaped air intake fitted to some carburettors.
   Found op http://www.encyclo.co.uk/visitor-contributions.php
   
   
2. 
   Bell Mouth
   The flaring or tapering of a machined hole, usually made at the entrance end because of misalignment or spring of the cutting tool.
   Found op http://www.diracdelta.co.uk/science/source/b/e/bell%20mouth/source.html
   
   
3. 
   Bell mouth
   In Building services engineering and HVAC, a bell mouth is a tapered expanding or reducing opening in the end of a ventilation duct, so named because the taper can resemble that of a bell shape. They are primarily designed and used for return air or extract air purposes within building ventilation ...
   Found op http://en.wikipedia.org/wiki/Bell_mouth
   
   

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