Source : Webster's Revised Unabridged Dictionary (1913)

Cheerer \Cheer"er\, n.
   One who cheers; one who, or that which, gladdens. ``Thou
   cheerer of our days.'' --Wotton. ``Prime cheerer, light.''
   --Thomson.

Source : WordNet®

cheerer
     n : a spectator who shouts encouragement