People who you work with that are more than colleagues but not quite friends. You really find them when you leave a company and you are deciding who gets the Facebook invite and who gets the LinkedIn invite.
My Frolleague, Bert, is really connected but I would not be seen dead with him at a bar, so I'll invite him to join my LinkedIn network. While I drink and work with Betty so she gets the Facebook invite.
(Noun)A friend who is also a work colleague. Frolleagues are often created during a particularly rowdy night of work drinks and are useful as a sounding board for bitching about your work load/boss etc.
A bunch of my frolleagues are going out for a pint tonight.