Just that, DVD-a, a multi-channel, multi-sample and bit rate capable DVD standard.
It's not very common, but it's in the DVD specification and allows masses of audio in lots of formats.
Course you'll need a player, but there are several combo DVD video and DVD-a machines around, we have two or three in the Uni.
If I can find the URL, I'll post a link to the DVD steering group site, all the info's there.