In many discussions about Batman and his abilities, prep time is always mentioned and emphasized.
What is this "prep time"?
Has it already been called as such in-universe?
What are some examples of this ability in use? (Comics, animation, etc. .)
Prep time - time to prepare
The point is that Batman can always overcome anything as long as he has time to analyze the threat and prepare for it accordingly. Examples can be found in comics such as:
To my knowledge, nobody called it "prep time" explicitly in the comics, but it probably is recognized by Batman's foes. Bane genuinely surprised Batman in the Knightfall and Joker in Death of the Family tends to plan against Batman's plans and gadgets (and gadgets are an embodiment of prep time).