Drinker
Part of speech: noun
Definition: Agent noun of drink; someone or something that drinks. Someone who drinks alcoholic beverages on a regular basis, especially when to an extent that is likely to impair his well-being.
Example sentence: I'm not a heavy drinker, I can sometimes go for hours without touching a drop.
Toper
Part of speech: noun
Definition: Someone who drinks a lot; a drunkard.