anonymous · adjective /əˈnɑn.ə.məs/
anonymous
C2 not giving a name
Dictionary examples:
an anonymous phone call/letter
The winner has asked to remain anonymous.
Learner example:
Because the internet does provide the possibility of staying anonymous, it is very hard to find the people wh[o] use it for illegal or criminal actions. (International English Language Testing System; C2; German)