Breasts large enough to resemble balloons, i.e. larger than normal bra sizes. Generally associated with people of the fat variety, though not always.
"Check out that chubba, she has some massive balloobs!"
by lolcatcatlol February 09, 2010
Balloobs are 2 balloons that are stuffed into someone's shirt and positioned side by side at chest level in order to resemble boobs.
That little girl is stuffing balloons up her shirt to make balloobs.
by TrigunBebopLover October 18, 2011