Source : Webster's Revised Unabridged Dictionary (1913)

Block \Block\, v. t. [imp. & p. p. {Blocked}; p. pr. & vb. n.
   {Blocking}.] [Cf. F. bloquer, fr. bloc block. See {Block},
   n.]
   1. To obstruct so as to prevent passage or progress; to
      prevent passage from, through, or into, by obstructing the
      way; -- used both of persons and things; -- often followed
      by up; as, to block up a road or harbor.

            With moles . . . would block the port. --Rowe.

            A city . . . besieged and blocked about. --Milton.

   2. To secure or support by means of blocks; to secure, as two
      boards at their angles of intersection, by pieces of wood
      glued to each.

   3. To shape on, or stamp with, a block; as, to block a hat.

   {To block out}, to begin to reduce to shape; to mark out
      roughly; to lay out; as, to block out a plan.

Blocking \Block"ing\, n.
   1. The act of obstructing, supporting, shaping, or stamping
      with a block or blocks.

   2. Blocks used to support (a building, etc.) temporarily.

Source : WordNet®

blocking
     n : (American football) the act of obstructing someone's path
         with your body; "he threw a rolling block into the line
         backer" [syn: {block}, {interference}]