had been ballooning

• past perfect progressive

  past perfect progressive

  Used to describe an action that was ongoing continuously in the past up until another past event interrupted it.

  of balloon.
  balloon

  noun

  a bag made of thin rubber or other light material, usually brightly colored, inflated with air or with some lighter-than-air gas and used as a children's plaything or as a decoration.

Related Words

• enlarge
• expand
• inflate
• swell