In Top Gun Maverick (2022), Maverick flies F14 and evades from enemy flight:
Maverick: Splitting the throttles. Coming around.
What does "Splitting the throttles" mean?
"Splitting the throttle" refers to the application of different power settings on the engines of the aircraft. In the case of the scene from Top Gun: Maverick, the afterburner on the left engine is cut (see image below).
Source: Top Gun Maverick
The purpose of this application of differential thrust is to enhance the yaw rate of the aircraft beyond what conventional control surfaces on the rudders of the aircraft could accomplish. This illustration (albeit for a commercial airliner) illustrates the forces that lead to increased yaw:
A neat breakdown of the manoeuvre from the movie is provided by a former airforce pilot on his YouTube channel: F-14 Split Throttle Dog Fight From Top Gun Maverick | Fighter Pilot Reacts
For some related discussions, see also:
Interestingly, differential thrust is now receiving increased attention from aerospace researchers for its potential application in electric aircraft with distributed propulsion systems. After all, if the entire leading edge of the wing is covered in small propellers, applying finely tuned amounts of differential thrust might be a useful part of maintaining directional stability in low-energy stages of flight.
It is not a figure of speech, "splitting the throttle" is quite literal. The throttle handle in the F-14 (and in many other aircraft with dual engines) consists of two levers, that control the amount of gas going to the left and right engine. You can see it in this picture:
Under normal circumstances you move the throttle as a whole, causing both engines to have the same level of thrust. But when you move them individually, you literally "split the throttles". This is normally only used when you start the engines (one by one) or in case of fuel or engine problems.
Theoretically it could be used for somewhat creative manoeuvring, almost like you have thrust vectoring, like what Maverick was doing in the movie, especially when you put one engine in afterburner and the other not (with all risks of a flame out), but in real life it was hardly (if at all) used for manoeuvring, as far as I know.