Source : Webster's Revised Unabridged Dictionary (1913)

Bump \Bump\, v. t. [imp. & p. p. {Bumped}; p. pr. & vb. n.
   {Bumping}.] [Cf. W. pwmp round mass, pwmpiaw to thump, bang,
   and E. bum, v. i., boom to roar.]
   To strike, as with or against anything large or solid; to
   thump; as, to bump the head against a wall.