an ‧ o ‧ nym ‧ i ‧ ty /ˌænəˈnɪməti, ˌænəˈnɪmɪti/ BrE AmE noun [uncountable]
when other people do not know who you are or what your name is:
Every step will be taken to preserve your anonymity.
One official, who spoke on condition of anonymity (=he would only speak if his name was not told) , said the White House took the threat very seriously.
the anonymity of city streets (=you do not know anyone, and no one knows you)