A
longman is typically an individual who chooses to
elongate a particular task for the purposes of irritation or general ignorance of surroundings. This keeps with a popular emerging British tradition to add man or similar as a suffix to a regular verb to form a compound word such as 'fuckboy, wasteman, roadman'.
In
Lehman's terms a longman is a man/women who takes overly long at any given situation with total disregard for responsibility.