'Bellwether' definitions:

Definition of 'bellwether'

From: WordNet
noun
Someone who assumes leadership of a movement or activity
noun
Sheep that leads the herd often wearing a bell

Definition of 'Bellwether'

From: GCIDE
  • Bellwether \Bell"weth`er\, n.
  • 1. A wether, or sheep, which leads the flock, with a bell on his neck. [1913 Webster]
  • 2. Hence: A leader. [Contemptuous] --Swift. [1913 Webster]

Synonyms of 'bellwether'

From: Moby Thesaurus