What does skunked beer taste like, How would you describe skunked beer?

The smell is hard to describe, especially to someone who grew up where there are no skunks. It is not really useful for me to tell you it smells like skunk musk. I have heard some of those people describe it as the smell of burnt rubber, body odor combined with burnt popcorn, sour coffee, or certain strains of aromatic marijuana.

You really have to try it yourself. You don't have to ruin a whole beer. Pick a very sunny day, and try pouring aboout four ounces of a really hoppy pale ale into a clear glass, covering it plastic wrap, and setting outside in the sun for 45 minutes (setting it indoors in the sunlight may not work as well because window glass blocks many UV rays). Now smell it and drink it. That is the smell of a dead skunk, run over by a car about a mile away on an Amrican country highway. And it is the smell of light-struck beer.

MBT (more often referred to as skunking or light-struck) is an off-putting flavor and aroma characteristic that is intuitively named after the animal which is well known for dispensing what is considered to be the Satan's post-apocalyptic butthole of all off-flavors. The chemical composition and odor of MBT (3-methyl-2-butene-1-thiol) is very similar to that of the anal secretion of a skunk.

The BJCP describes and explains the light-struck off-flavor as the following:

This aroma and taste is due to the presence of the same mercaptans that are found in the scent glands of skunks. These compounds are formed when ultraviolet light cleaves an isohumulone molecule, and the resulting radical combines with a sulfur compound. Beer stored in clear or green glass bottles is more susceptible to this reaction, which is why brown glass offers more protection. Lightstruck flavors are not desirable in any style, but many European imports possess this quality. Note that Miller Brewing is able to use clear glass bottles because they use a chemically modified form of isohumulone that does not interact with light.