The Collaborative International Dictionary of English v.0.48:

Scrimmage \Scrim"mage\ (?; 48), n. [A corruption of skirmish.
   "Sore scrymmishe." --Ld. Berners.] [Written also
   scrummage.]
   1. Formerly, a skirmish; now, a general row or confused fight
      or struggle.
      [1913 Webster]

   2. (Football) The struggle in the rush lines after the ball
      is put in play.
      [1913 Webster]

WordNet (r) 3.0 (2006):

scrimmage
    n 1: (American football) practice play between a football team's
         squads
    2: a noisy riotous fight [syn: melee, scrimmage, battle
       royal]
    v 1: practice playing (a sport)

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "scrimmage":
   action, aerial combat, affray, armored combat, battle,
   battle royal, brawl, broil, brouhaha, brush, bullfight, clash,
   clash of arms, cockfight, combat, conflict, disturbance, dogfight,
   donnybrook, donnybrook fair, embroilment, exchange of blows, fight,
   fire fight, fracas, fray, free-for-all, ground combat,
   hand-to-hand combat, hand-to-hand fight, house-to-house combat,
   knock-down-and-drag-out, melee, naval combat, passage of arms,
   pitched battle, quarrel, riot, row, ruckus, ruction, rumble,
   rumpus, running fight, scramble, scrap, scuffle, set-to,
   shoving match, skirmish, stand-up fight, street fight, struggle,
   tauromachy, tug-of-war, tussle