It's a more eclectic way of referring to one's personal sense of style or fashion.
If someone asked how these shoes look with these pants, the boring word is nice, great, etc. If the shoes absolutely make the pants come to life to the point that the pant's won't let you take them off, doesn't that deserve a colorful reference that matches the feeling it gives me. I'd say.."The way that those shoes are wearing those pants are fantasciously(fan-tast-ish-lee) fucking wicked!!"
When I met up with Barbie & Renee at the mall there was something that was contagiously sparkley about them. When Renee stopped talking mid-sentence and darted off straight for a special section of shoes and picked up the most "fashion-sexy" vintage styled high heel stiletto boot that actually featured a peep-toe in the front. Her "fashion-sexy" at that moment blew me away and made us both tingle all over our bodies.