Super Lydian
Super Lydian is a phrase popularized by Jacob Collier[1] to describe chords with the "♯15" extension, as well as the scale that gives rise to such chords. The idea behind Super Lydian is that it gets brighter and brighter the further you go up.
Background
At a basic level, the Super Lydian sound comes from stacking perfect fifths. Stacking them from the root (C-G-D-A-E-B-F♯) results in the set of notes in the Lydian scale. Extending the sequence (C-G-D-A-E-B-F♯-C♯) reveals a new brighter note directly outside of Lydian, commonly referred to as the ♯15. The ♯15 chord-extension is the same note as the ♭9, but always called a ♯15 in the context of the Super Lydian chords.
Other compacted patterns that result in a Super Lydian sound include stacking major and minor thirds from the root (C-E-G-B-D-F♯-A-C♯) and the Super Lydian scale, built from stacking Lydian tetrachords (C-D-E-F♯-G-A-B-C♯).
Super Ultra Hyper Mega Meta Lydian
Extending any of these patterns beyond the ♯15 to reach the “♯19” results in an "Ultra Lydian" sound. Endlessly extending any of the patterns results in what’s referred to as "Super-Ultra-Hyper-Mega-Meta-Lydian".