pseudonym

n. fictitious name; pen name, name used by an author in place of his real name; assumed name

A pseudonym (, pseudo + -onym: false name) is an artificial, fictitious name, also known as an alias, used by an individual as an alternative to a person's legal name. In most legal systems, a name assumed for a non-fraudulent purpose is a legal name and usable as the person's true name, which is however preferred or required for various official purposes. The most common example is when a woman assumes her husband's surname without resorting to the formal statutory process (i.e. by petitioning a court; a few American states have a statutory provision for recording a new name at marriage.) Note that in some States only the given and surnames form the legal name; "a middle name or initial is not material in any legal proceeding". A pseudonym is distinct from an allonym, which is the name of another actual person, usually historical, assumed by someone in authorship of a work of art; such as when ghostwriting a book or play, or in parody, or when using a front such as by screenwriters blacklisted in Hollywood in the 1950s,  1960s and 1970s. Someone who is pseudonymous is someone who is using a pseudonym. The opposite is anthroponym, meaning a full legal name or some recognisable shortened form of it such as Fred Smith for Frederick John Smith, with or without titles.
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Noun
1. a fictitious name used when the person performs a particular social role
(synonym) anonym, nom de guerre
(hypernym) name
(hyponym) stage name

n. pseudonym, fictitious name, pen name, name used by an author in place of his real name, assumed name

adj. pseudonymous, written under an assumed name

(n.)
A fictitious name assumed for the time, as by an author; a pen name.