A half-gallon (64 ounce) jug sold by small breweries and brewpubs for take-out purposes. Typically adorned with the label of the brewery/establishment it came from. Most breweries/brewpubs will only refill their own growlers. Not to be confused with it's little cousin the 32-ounce howler.
Man I got this growler from the pub last night, it's already flat.
"Where's your growler?" (As used in Russ Meyer film, 1969 by Charles Napier, actor of sorts, enquiring for the lavvy at a petrol station - or gas if you prefer).