I keep coming across the term "bubble pushing in logic gates."
Bubble Pushing(or Bubble-to-bubble convention/ Bubble Matching)

I'm not sure if this what you are referring to, but that's what googling 'bubble pushing' yielded. I've personally never heard this term before.


  Bubble pushing is a technique to apply De Morgan's
  theorem directly to the logic diagram. 
  
  
  Change the logic gate (AND to OR and OR to AND).
  Add bubbles to the inputs and outputs where there were none, and remove the original bubbles.
  
  
  Logic gates can be De Morganized so that bubbles appear on inputs or outputs in order to satisfy signal conditions rather than specific logic functions. An active-low signal should be connected to a bubble on the input of a logic gate.


According to this, it's just a visual way of performing de Morgan's theorem vs doing it on paper with boolean algebra.