Any item or items used in one's yard, in abundance, for ornamental and decorative purposes that would be considered trashy by most peoples standards. It is a combination of the words yard and garbage. It is not to be confused with items often found in a hoarder's yard, as that is simply trash.
Her yard would look so much better if she didn't have so much yarbage. Who decorates their yard with flamingos and gnomesanyway?