noun
heavy drinker; boozer; tippler
A somewhat colorful or slangy term for someone who drinks a lot, often with a sense of expertise or dedication to drinking. Not a formal medical term.
彼は有名な飲み師で、毎晩のように酒場に現れる。
He's a well-known heavy drinker who shows up at bars almost every night.
あの呑み師は一晩で一升瓶を空けるらしい。
That boozer apparently empties a whole 1.8-liter bottle in one night.
Compound of 飲み (nomi, 'drinking', the continuative form of 飲む 'to drink') and 師 (shi, 'master, expert'). The variant 呑み師 uses the alternative kanji 呑む for drinking. The abbreviated forms 呑師 and 飲師 drop the okurigana.