balloon in WordNet English dictionary

1. large tough nonrigid bag filled with gas or heated air
   balloon 
   
2. small thin inflatable rubber bag with narrow neck
   balloon 
   

1. become inflated
   "The sails ballooned"
   balloon  inflate  billow 
   
2. ride in a hot-air balloon
   "He tried to balloon around the earth but storms forced him to land in China"
   balloon