Thirst is the body's natural signal for needing fluids, but excessive or persistent thirst can sometimes point to an underlying issue. Knowing the causes, how it's diagnosed, and the right treatment can help manage it effectively and keep the body properly hydrated. Find out about excessive thirst , including what might be causing it, when to see a GP and the difference between dry mouth and excessive thirst . The meaning of THIRST is a sensation of dryness in the mouth and throat associated with a desire for liquids; also : the bodily condition (as of dehydration) that induces this sensation. (Definition of thirst from the Cambridge Academic Content Dictionary © Cambridge University Press)