I like to use "harsh", because "bitter" for me would be reserved for burnt coffee
Or I explain the bitterness, like "bitter like a cumquat fruit, or a grapefruit - that's a good bitterness. Some people think dark chocolate is bitter - bittersweet chocolate.
So if I use the word, I compare it with other foods....
just my 2 cents
Joey
PS.: I hate it it when people in my shop who usually don't drink espresso have a coffee-testing, and after drinking the espressos which are totally different, someone says "to me they are all bitter" ... AAARRRGHHH
People often don't know the right words for taste. They only know salty, sweet, sour and bitter.
Therefore I let them smell my aroma bottles first to try to differ between flavors, and let them think about fruits, and vegetables and plants and spices before testing the espressos.....
rant over