Hang-er, perhaps some of your confusion comes from the varied terminology in common use.
A good overview of the problem, with certification definitions is given in
NPA_14_2004 Operations on Contaminated Runways. There is also a good briefing in the UK CAA AIC (Pink 4P111/07) – registration required at
http://www.ais.org.uk/aes/login.jsp . See “Runway Operations - Risks and Factors Associated with Operations on Runways Affected by Snow, Slush or Water”.
Use of the description ‘slippery’ adds confusion; it is not a certification term. However, it is used as an ATC runway maintenance description for runways which have less than the desired coefficient of friction when wet; this is advisory information for pilots. Unfortunately, Boeing and other people in the industry also use the term (without definition) for generic ‘contaminated’ runway operations.
An operational overview of some of the aspects for landing is in
Managing the Threats and Errors of Approach and Landing.