Guys who are so uptight they tuck in their shirts when it's not formally necessary. eg- a job interview or business meeting. Men who think it's proper to tuck in their polo or t-shirt when they're in a casual dress situation. eg- a party.
A TUCKIE is a selfie where a man tucks his penis for a full body pic (a la "Buffalo Bill"). The tuckie is popular amongst customers of Vagabond Saints/VSTL Vestments (Started by the one called "Mike").