The Collaborative International Dictionary of English v.0.48:

monicker \monicker\, moniker \moniker\n.
   The name of a person, especially an alias or a nickname.
   [slang]

   Syn: nickname, alias, sobriquet, cognomen.
        [PJC]

WordNet (r) 3.0 (2006):

moniker
    n 1: a familiar name for a person (often a shortened version of
         a person's given name); "Joe's mother would not use his
         nickname and always called him Joseph"; "Henry's nickname
         was Slim" [syn: nickname, moniker, cognomen,
         sobriquet, soubriquet, byname]

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "moniker":
   appellation, appellative, binomen, binomial name, byname, byword,
   cognomen, cryptonym, denomination, designation, empty title,
   epithet, eponym, euonym, handle, honorific, hyponym, label, name,
   namesake, nomen, nomen nudum, proper name, proper noun,
   scientific name, secret name, sobriquet, style, tag, tautonym,
   title, trinomen, trinomial name