Definition of balloon noun from the Oxford Advanced American Dictionary

balloon

noun
/bəˈlun/
 
 
1 a small bag made of very thin rubber that becomes larger and rounder when you fill it with air or gas. Balloons are brightly colored and used as decorations or toysto blow up/pop a balloonMy balloon has burst!A thousand balloons were released to mark the event. compare trial balloon2 = hot-air balloonIDIOM

go over like a lead balloon

(informal) to be very unsuccessful; to not be accepted by peopleMy suggestion went over like a lead balloon.go over like a lead balloon