Ordinal collapsing function

In mathematical logic and set theory, an ordinal collapsing function is a technique for defining certain recursive large countable ordinals, whose principle is to give names to certain ordinals much larger than the one being defined, perhaps even large cardinals, and then "collapse" them down to a system of notations for the sought-after ordinal. For this reason, ordinal collapsing functions are described as an impredicative manner of naming ordinals.

This keyword could refer to multiple things. Here are some suggestions: