According to http://www.wisegeek.com a conniption fit is described as:
Assume for a minute you decided to tell your parents about your plans to ditch college and join the circus. The next event you witness should qualify as a conniption fit. A conniption fit is a sudden, violent emotional outburst generally triggered by shocking news or an unexpected turn of events. Unlike a tantrum, which could be triggered with little outside provocation, a conniption fit is often an anticipated response to incredibly bad or disappointing news. A conniption fit is generally characterized by a tirade of strong language accompanied by signs of frustration, rage and/or sadness. Sometimes a person having a conniption fit is reduced to stutters and incomprehensible epithets.