A Square John is slang meaning a reliable trust worthy guy. The term originated from Bike Gangs and is common in the Canadian Prison system. It is considered to be a compliment if you are referred to as a Square John
He's cool man, don't worry he's a Square John.
by John-999 January 31, 2011
n. a lame-o, or. someone who displays no signs of hipness or sense of adventure whatsoever; a person who is overtly conservative, often likely to be a narc; a gaynal
Why did you ask Jason to party with us tonight? He is such a squarejohn; I heard he ratted out Phil for having a dimebag in school.
by Lord Gaynal September 26, 2006