Sub-Prime

category of Mortgage Debt - where lender is higher-risk than "normal"

http://en.wikipedia.org/wiki/Subprime_lending

often structured as an ARM (Adjustable Rate Mortgage), with an initially low interest rate (partially due to low Fed rates at the time, partially due to marketing Bait And Switch)

another Credit Rating failure in 2006-8

part of Credit Crisis 2008