XD or xD is actually an emoji used in chat lines with ‘X’ being the eyes and ‘D’ being the mouth, to make a seeming of the person having squinched eyes and a mouth wide open laughing.
Well to be adjacent to or within the general vicinity of an xd usually implies that there has been a humorous event, occurance or a percievedly outlandish and funny joke that was just told. I would advise inquiring to hear the joke if you're near an xd once again.
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