The rarely used name of the opening in male "brief" style underwear. Ostensibly for accessing the penis for urination, it is used for this purpose by less than ten percent of the male brief wearing population. The vast majority tend to use the easier and more practical "over the top" method. Named for it's inventor, Augustus Archibald Von Gleeson.
Despite his clever use of the gleeson area to hide his weed, the police found it and charged him with possession.