The Collaborative International Dictionary of English v.0.48:

Slap \Slap\, v. t. [imp. & p. p. Slapped; p. pr. & vb. n.
   Slapping.]
   To strike with the open hand, or with something broad.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Slapper \Slap"per\, Slapping \Slap"ping\, a.
   Very large; monstrous; big. [Slang.]
   [1913 Webster]