retroduce
v. - the act of introducing yourself to someone you've already met. It can occur under a variety of circumstances, but is usually undesirable. A few common situations are as follows.
1. You have met the person, but do not remember having met them, or do not remember their name. This version of retroducing usually leads to an awkward, detailed retelling of how you met, while you listen and feel like a jackass.
2. You have met the person, but you do no think that they remember you, so you introduce yourself again. You are forced to decide how to explain yourself, whether you would have them think that you are absentminded, rude, or that you consider yourself to be completely forgettable.
Hi, I'm Mark." "Oh, hi Mark, it's Lisa. Don't you remember me from Jonny's birthday party, we talked for a while about the pros and cons of HD versus 35mm formats." "Oh, sorry, I didn't mean to retroduce myself.