I know that cuvée is wine produced from several types of grape. Is there a word to describe wine made from a single type?
A cuvée usually means that the wine if made from the same batch of grapes, harvested at the same time (year), from a particular plot of land.
A cuvée can either be a single grape varietal , which is called a mono-varietal cuvée or different varietals, which is usually called a blend.
For example, a Bordeaux wine can be made with different grapes varietals (merlot, cabernet franc, cabernet sauvignon...); the Bordeaux AOC allows such blends.
On the other side, the Burgundy wines, are mono-varietals, they only allow for Pinot Noir for the red wines and Chardonnay for the whites (*)
(*) There are other types of grapes, like gamay and aligoté, but still, they will not be blended (AFAIK).
Sometimes, cuvée is used in association with the vintage (year) of the wine.
People will say "the cuvée 2015 of such and such wine is more rounded than the cuvée 2017, because the weather was dryer"
A varietal is a wine made from a single type of grape.