https://blog.nowhere.moe/opsec/anonymityexplained/index.html
Anonymity is the absence of Identification (or Onymity), it is when individuals are indistinguishable from each other, they all look the same.
DISCLAIMER: That Someone remains Anonymous UNTIL THEY MAKE ONE OPSEC MISTAKE !
Keep in mind that maintaining Anonymity is a much stricter practice than that of maintaining Privacy, as you will see, more threat vectors come into the picture.