An individual who has allowed ones occupational environment define ones personality, to the point of behaving as if one is always within the four walls of an office.
That's just how squares are! They take everything serious, can't relax, and don't know how to have fun.
1) A shape with four sides, the sides are all the same left and all interior angles are 90 degrees
2) Someone who if their parents knew every intricate of their lives the parents wouldn't be to upset or concerned
"Wow you have cut your piece of paper into a square"
a) "Sally is such a square"
b) "Yeah but I bet her parents are proud"
a) "Wish she would have some fun sometimes though"