Source : Webster's Revised Unabridged Dictionary (1913)

Sprack \Sprack\, a. [Cf. Icel. spr[ae]kr sprightly, dial. Sw.
   spr["a]k, spr["a]g, spirited, mettlesome; or Gael. spraic
   vigor.]
   Quick; lively; alert. [Prov. Eng. & Scot.]