Austere is a major geek term that is often used to describe a young, expensive wine that critics assume will evolve into a blockbuster.
The term austere is actually difficult to pinpoint; it is a vague definition of a wine that has a high level of acid and/or tannin, which currently overpowers the fruit, but is expected to soften with age.
For example, a huge red Bordeaux or expensive California Cabernet may taste more like an ashtray than wine — when it is young. The flavors will be dominated by bitter earth and tar, acids may be oppressive (some people describe it as “bite”), and/or the tannins may leave your tongue feeling like it needs a shave. However, experienced connoisseurs — who have tasted similar wines in youth and later at maturity — may take the educated guess that the wine will eventually evelve into something much more drinkable. So instead of saying the wine is similar to licking hot tarmac, they'll say it is “austere” (sounds a lot better, doesn't it?).
In all seriousness, if you hear or read the word “austere” in tasting notes, it almost always will mean that the wine is 1) expensive; 2) very young; and 3) after appropriate time in the cellar, the “hardness” (“hard” is a common synonym for “austere”) will soften, the fruit will come forward, and the wine should taste somewhere between good and extraordinary.
By the way, if you are an advanced wine drinker and want to become more knowledgeable about wine, you should consider purchasing The Oxford Companion to Wine. Just about every wine term you've ever heard (and never heard) is defined in this massive tome, and it makes a nice paperweight. Click on the picture to the left to buy it from Amazon.