balloon
/bəˈlun/
noun
A brightly colored rubber sac that is inflated with air and then sealed at the neck, used as a children’s toy or a decoration.
the room was festooned with balloons and streamers
intransitive verb
Swell out in a spherical shape; billow.
the trousers ballooned out below his waist
swell,swell out,puff out,puff up,bulge,bulge out,bag,belly,belly out,fill,fill out,billow,billow out