I wasn't going to bring this up until I ran across this amazing response on the Escapist Forum:
Let me make the distinction clear for the hangers-on who jumped straight from the short bus into my hobby:
Hardcore - people who keep buying games out of some idiotic habit despite needless complications with hardware, absurd prices, disappointing "AAA" wankfests and/or thoroughly corrupt review industry who seem to have an extreme aversion toward actually fulfilling their function
Casual - everyone else
So, "casual" is at best a useless synonym. "Not retarded" works well enough that we really don't need to coin a new term.