1. 
   underflow
   (programming) (or 'floating point underflow', 'floating underflow', after 'overflow') A condition that can occur when the result of a floating-point operation would be smaller in magnitude (closer to zero, either positive or negative) than the smallest quantity representable. Underflow is actually ...
   Found op http://foldoc.org/underflow
   
   
2. 
   Underflow
   The dominant flow of two confronting flows, over the other. The lesser flow reverses direction giving poor surface appearance and structural strength. Underflow should be avoided by positioning gates so that the flow fronts meet at the end of filling.
   Found op http://www.blowmachines.com/glossary1.htm
   
   

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