n. IBM's SNA (Systems Network Architecture), an incredibly losing and bletcherous communications protocol widely favored at commercial shops that don't know any better. The official IBM definition is "that which binds blue boxes together."
See fear and loathing.
It may not be irrelevant that Blue Glue is the trade name of a 3M product that is commonly used to hold down the carpet squares to the removable panel floors common in dinosaur pens. A correspondent at U. Minn. reports that the CS department there has about 80 bottles of the stuff hanging about, so they often refer to any messy work to be done as 'using the blue glue'.