A dolor is a unit of pain used by utilitarians. A utilitarian will probably grant you that saying something like: "Burning my hand gives me five dolors of pain, but having a close friend die gives me ten thousand dolors of pain." sounds completely arbitrary. They don't really want to imply that this is actually some kind of perfect objective measurement. What a utilitarian really wants to say here is that having a friend die is two thousand times more painfull than burning your hand.

Dolors are often used in conjunction with hedons in examples of hedonistic calculus. For example: "drinking heavily may give me 30 hedons of pleasure now, but between the vomiting and the hangover I will get 50 dolors of pain. I net 20 dolors of pain, therefore I should drink moderately."