Love this thread! Along with the abbreviations thread referenced here, it'll save noobs like me hours of random reading and googling. (Don't ask how I know) :-) I particularly liked the VE entry. I'll try to add what I can.

Delta: A mathematical term referring to the difference between two readings such as ambient air pressure vs manifold absolute pressure, or the reading between the first and second O2 sensor. Or the difference between coolant temperature at two points in the flow circuit. The quantitative value of the difference is used in calculations the ECM or PCM uses to optimize the setting of another component or calculation.