Coffee cupping is an umbrella with many different expressions under it. Since coffee cupping is tasting coffee, the terms are often descriptions that help define the flavors and nuances of individual coffees.
What is bitter?
Bitter is one of the five basic tastes, and it is also a taste that can be used to describe coffee.
Some like it, like when you sip tonic. Others associate it with cold coffee. There can be several reasons why coffee is too bitter. It may be because the water you have brewed with is too hot. It may also be because the coffee is overextracted.