Shatnez שַׁעַטְנֵז is cloth containing both wool and linen, which the law, prohibits wearing.
🔥 Deuteronomy 22:11
Thou shalt not wear a garment of divers sorts, as of woollen and linen together.
💡 Wool and linen attached to each other by any means is forbidden. It does not matter whether they are sewn together, spun, twisted, glued, or any method of attaching whatsoever. Any method of combining wool and linen is forbidden by God Most High.