bsieker
I'm not sure about the term, either, but the MD80's JT8D-200 engines, being mechanically controlled (non-FADEC), can deliver more than maximum rated thrust, if needed. This is called "MAX THROTTLE", and should be limited to stall and wind shear recovery at low altitudes; a normal go-around should not require more than maximum rated thrust.
Here's an excellent chance for you to learn something and perhaps to share it with the rest of the forum
Do a google search on MD80
reserve thrust (excluding all flight sim products).
This neat little feature doesn't need pilot input, it simply looks for differences between engines of 10% or so.