you've certainly heard the word, perhaps used it. or seen the concept portrayed in film or television. the main characters in the sitcom seinfeld all believed they had theirs and in one episode they (or was it just elaine?) meet face to face.
the compact oxford english dictionary defines it as an apparition or double of a living person; thomas gale as follows:
«(also known as the double.) a literary technique by which a character is duplicated (usually in the form of an alter ego, though sometimes as a ghostly counterpart) or divided into two distinct, usually opposite personalities. the use of this character device is widespread in nineteenth- and twentieth-century literature, and indicates a growing awareness among authors that the "self" is really a composite of many "selves." a well-known story containing a doppelgänger character is robert louis stevenson's dr jekyll and mr hyde, which dramatises an internal struggle between good and evil.»
it seems, that either by coincidence or design, i've got one running about the nation's capital, fond of eating out and parties at places to which i've never been and with people i don't know nor have ever met. a couple of weeks ago an aquaintance swore, not only that he'd seen me at the restaurant where he know works, but that we'd spoken. impossible. and just tonight, this other chap, apparently mistaking me for someone else, although i really don't know how this could happen, mentioned talking to so-and-so and inviting someone else to a birthday celebration neither of whom i've met in my entire life. the chap telling the story, confronted with this fact alleged seeing me at the one person's social gatherings all the time, yet another person i don't know and have never met. hadn't even heard the names until this evening. how the chap i was talking to could make this mistake is really surprising, for he knows exactly what i look and sound like even if we're barely acquainted.
coupled with receiving unsolicited and unexpected IMs from people introducing themselves using my name seems to make the matter feel like a tad more than just creepy coincidence, which is what i'd certainly expect it all to be.
just in case, let's then invite the deus ex machina to interfere... :-).