When you have excessive thirst it means that you cannot get hydrated properly even though you drink several glasses of water or liquids throughout the day.
If you're drinking enough liquids including water and are still very thirsty after drinking the water or liquids then you likely have excessive thirst.
Excessive thirst can be caused by medical conditions such as diabetes and when you have diabetes and have high blood sugar levels that can cause excessive thirst.
Some medications you take can also be a cause of excessive thirst and dry mouth as well so I would speak with your doctor and let them know you have excessive thirst even after you drink plenty of water and other liquids.
Excessive thirst is not normal always and can sometimes be caused by medical conditions or even just medications you take.