Without giving a name.

Person whose name is not given; pseudonym
Anonymous person; pseudonym.

ETYM Greek, nameless; an priv. + onom name + -mity.
The state of being anonymous; SYN. namelessness.
The ability to send an e-mail message or an article to a newsgroup without one’s identity becoming known. Ordinarily, the e-mail address of the sender appears automatically in a message’s header, which is created by the client software. To achieve anonymity, a message must be sent through an anonymous remailer—which, however, maintains a record of the sender’s identity to enable replies. See also anonymous remailer.

State of being unknown, namelessness