The Collaborative International Dictionary of English v.0.48:

Spank \Spank\, v. i.
   To move with a quick, lively step between a trot and gallop;
   to move quickly. --Thackeray.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Spank \Spank\ (sp[a^][ng]k), v. t. [imp. & p. p. Spanked
   (sp[a^][ng]kt); p. pr. & vb. n. Spanking.] [Of unknown
   origin; cf. LG. spakken, spenkern, to run and spring about
   quickly.]
   To strike, as the breech, with the open hand; to slap.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Spank \Spank\, n.
   A blow with the open hand; a slap.
   [1913 Webster]

WordNet (r) 3.0 (2006):

spank
    n 1: a slap with the flat of the hand
    v 1: give a spanking to; subject to a spanking [syn: spank,
         paddle, larrup]