Short for Dan's Competition.
A mail order BMX parts shop that is overpriced and impossible to order parts that will fit your current bike with out first going through costly trial and error purchases trying to find a part that fits.
Buying from Dan usually results in a collection of really nice expensive bike parts in your closet instead of on your bike.
Buying form Dan's Comp also results in days spent on Urban Dictionary.com anonymously whining instead of days spent riding
Jokes on Dan's comp however, because in a hundred years my collection of antique bike parts will be so valuable I'll be able to buy the companies suppliers and I'll stop selling to Dan's and shut it down forever! *evil Laugh*