I was quite surprised Matt has not come across this term before, it might be a European thing but it was a hot topic in the pits at any race meeting throughout the 80s. The term was/is used to describe wheel travel vs damper travel, ie if 2" of wheel travel resulted in 1" of damper travel the suspension was said to have a 2:1 motion ratio. The term was actually used much more around inboard damper suspension systems with bell-cranks used to amplify the motion ratio aka "rising rate" . Simply put it might be something like this, the first 2" of wheel travel results in 1" of damper travel, the second 2" of travel results in 1.5" at the damper and so on.