A Full Quad or Unicorn Quad is a polyamorous relationship between four people where all four people are dating each other. This can be considered a mix of a group relationship and a quad relationship.
Flag
The flag was coined by Tumblr user beyond-mogai-pride-flags on November 17th, 2018.
Resources
https://beyond-mogai-pride-flags.tumblr.com/post/180196429235/unicorn-quad-pride-flag