noun
heavy drinker; drunkard; tippler
Colloquial, often affectionate or teasing term for someone who loves to drink, not necessarily an alcoholic.
うちの父は大の飲み助で、毎晩晩酌を欠かさない。
My father is a big drinker and never misses his evening drink.
彼は飲み助だが、仕事には真面目だ。
He's a heavy drinker, but he's serious about his work.
Compound of 飲み (nomi, 'drinking', continuative form of 飲む) and 助 (suke, a suffix often used in personal names or to indicate a person with a certain trait). The exact origin is uncertain, but it likely arose as a playful nickname for a drinking companion.