noun (n)

• an act so striking or impressive that the show must be delayed until the audience quiets down(noun.communication)

  Synonym:
  show-stopper, stopper
  

  source: wordnet30
• something that is strikingly attractive or has great popular appeal(noun.attribute)

  Example:
  The brilliant orange flowers against the green foliage were a showstopper.
  

  Synonym:
  show-stopper
  

  source: wordnet30