noun
drinking buddy; drinking companion
A friend or acquaintance with whom one regularly drinks alcohol. Casual, friendly term.
彼は大学時代からの飲み仲間だ。
He's been my drinking buddy since college.
週末はいつもの飲み仲間と居酒屋に行く。
On weekends I go to an izakaya with my usual drinking companions.
Similar meaning, but 飲み仲間 implies a closer, more regular drinking relationship, while 飲み友達 can be more casual.
Compound of 飲み (nomi, 'drinking', continuative form of 飲む) + 仲間 (nakama, 'companion, group').