the beer you carry around, but don't drink, to ensure that no one else offers you another; usually when you've "had enough"
Person: How did you manage not to get trashed like everyone else last night?
You: I had my cover beer around the end of the night.
Or
Friend: How about another beer?
You: Nah, cover beer.
You: I had my cover beer around the end of the night.
Or
Friend: How about another beer?
You: Nah, cover beer.
by USANZ September 8, 2009