Deceived by a man's appearance into thinking he is a she. To get shimmed or be shimmed is to check out what seems to be a hot chick but turns out to be some fuckin' dude. She is in fact a him; hence, to be shimmed. Transvestism is not necessary for shimming, which more often occurs in everyday situations with long-haired males, sometimes but not always driving in that Jag convertible up ahead in the next lane. To be shimmed is always painful, but is made most acute by grizzled facial hair and direct eye contact with the shim.
Dude, I got brutally shimmed driving in to work today. Saw this hot skinny jogger in gold spandex leggings but when I got around to the front it was a fuckin' sunbaked old man! Goddamnit!