“big
rubble tubble” is the adjective part of
the definition, but “big rubble tubble bitch” is the whole
definition. Can be used as an adjective or noun. Describes a “bitch” who is so big (s)he looks like they’re about to “tubble” (tumble) over, and/or looks like a pile of rubble. Can be derogatory but is usually in a joking manner.