Non-Denary (Sometimes shortened to ND* or Endy) is any type of gender that doesn't fit fully in the Denary Genders, the first ten genders. Someone who is non-denary may not identify as 100% male, 100% female, 100% agender, etc. But a combination or something different than those. Non-Denary people also fit in the Non-Binary category, since they do not fully identify as fully male or female.
*not to be confused with neurodivergent, which can also be shortened to ND.
Etymology
Denary (Or decimal) is the name of a base-10 number system, similar to how binary means a base-2 system.