This is the description given to an object when it is selected in the loadout Store. To use it, enter one of the names from ObjDescs.str in the Strings\<language>folder (e.g. use_blackjack).
As with Inventory->Object Name, an item can be given a custom description by using quotations, like this:
use_bob: "Bob is a cook for hire who is willing to tag along for a reasonable price. Cost:200"
Property Name: GameDesc