Bibulous describes a person who likes to drink too much alcohol. It is an old, rather literary adjective, and today it often comes with a small smile — a polite or joking way to say someone drinks a lot, instead of calling them a drunk. You will almost never hear it in the street or in a teenage chat. It turns up in novels, witty columns, and when a speaker wants to sound dry and clever. Though actually, the Latin parent just meant “fond of drinking,” not only wine and beer; English has narrowed it to alcohol, and to that slightly comic, raised-eyebrow tone. It is not a kind word if you say it straight at someone who has a real drinking problem, but in print it is often softer than drunkard.