Definitions?

[Actor]

In Figure Handicapping James Quinn uses the term "back class" but doesn't seem to define it.
William L. Scott attributes the term "big win" to Tom Ainslie. In perusing Ainslie's work I do find the term but again I can't find a definition.

[thaskalos]

In Figure Handicapping James Quinn uses the term "back class" but doesn't seem to define it.
William L. Scott attributes the term "big win" to Tom Ainslie. In perusing Ainslie's work I do find the term but again I can't find a definition.
BACK CLASS: Former class. The horse shows a victory in a prior past-performance...in a higher class race than the one being handicapped today.

BIG WIN: The horse leads, or is within two lengths of the leader at the stretch call...and then gains ground from there to the wire, and wins by at least 2 lengths.

[Actor]

Thanks!