GIGABOUT: 2^30, which is 1,073,741,824, or about one billion

(the way a Meg is 2^20, which is 1,048,576, or about a million,
and a K is 2^10, which is 1,024, or about a thousand)

Edit: Oops, that's two changes. One too many. Let's try this one:

GADABOOT: to kick your prodigal son out of the house once and for all