The word is composed from two other: Quilt and Minecraft. It is often simply shortened as "Quilt".
Quiltmc is a modloader for the game Minecraft, split from the Fabric modloader, after those were accused of being too based (which is not true, but the split happened). Quiltmc characterizes itself by being unfinished, it's however mitigated by the dilligent efforts of the moderation team to keep the community very happy - in short, maintaining basedness levels at a minimum, not even fearing drastic, quasi fascist measures, to keep based elements out.

The community itself is majorly composed of white beta males, also known as "Mayoids", thus guaranteeing constant and very curageous simping to groups of people who do not even know what a "Minecraft mod" is, let alone Quiltmc.
- Have you been banned from Quiltmc again?
- Yes, I posted something sarcastic in a completely unrelated Discord server.
by xabedo#4042 August 23, 2021
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A very popular definition in the Urban Dictionary, where people whose feelings got hurt by a Minecraft modloader go to cry about it.
Man 1: Ha! I went on the quiltmc modloader page on UD and wrote about how unbased it is. Totally owned them!
Man 2: Please, get a life.
by RevTecCom January 19, 2023
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Haha, funny modloader go brrr.

Honestly though - please reconsider your choices if you thought making an entirely new modloader because your personal feelings were offended.
Whenever I think I'm useless, I look towards quiltmc
by oio010 September 16, 2021
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Quilt is a mod loader for Minecraft forked from the Fabric project.
Are you using fabricmc?
No, quiltmc
by EFrost March 14, 2022
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