Definition of Survival Skills
"Survival Skills" lacks a dictionary definition, so i'll give you mine: "The skill set required to be able to survive any event, unexpected or otherwise".
Often preceding "survival skills" we'll find a word defining the specific unexpected event or situation:
Wilderness Survival Skills
Urban Survival Skills
Disaster Survival Skills
Earthquake Survival Skills
Nuclear Survival Skills
And more. Although there are specific skills and knowledge required for each type of event, many skills are universal.