labored and dull; "a ponderous speech"

Ponderous is often used as a synonym for massive, but in my usage a massive wine is simply a big, rich, very concentrated wine with balance, whereas a ponderous wine is a wine that has become heavy and tiring to drink.

Even less balanced than a "hearty" or "sturdy" wine. The sole impact is one of high alcohol and "body" character. Little or no acid/tannin content. An everyday red wine, similar to a french "vin ordinaire" country wine sold by alcohol content, can be an example.