Acronym for "short sleeve button-up." Used in a variety of fashions, most commonly for vacations, blue collar jobs or for a lack of better taste.
The SSBU is often worn in environments where class is non-existant and is often accompanied by its cousins, the jort or the cargo pants. SSBUs are often found in Hawaiian print or with the name of the individual patched over the chest. SSBUs are never appropriate for business attire and should never be tucked in or worn with a tie.
Ross was reprimanded this morning for wearing an SSBU to a board meeting.