Source : Webster's Revised Unabridged Dictionary (1913)

Slape \Slape\, a. [Icel. sleipr slippery; akin to E. slip.]
   Slippery; smooth; crafty; hypocritical. [Prov. Eng.]

   {Slape ale}, plain ale, as opposed to {medicated} or {mixed}
      ale. [Prov. Eng.]