1. [n]  the act of pounding (delivering repeated heavy blows); "the sudden hammer of fists caught him off guard"; "the pounding of feet on the hallway"
2. [n]  a hand tool with a heavy rigid head and a handle; used to deliver an impulsive force by striking
3. [n]  a power tool for drilling rocks
4. [n]  a striker that is covered in felt and that causes the piano strings to vibrate
5. [n]  the part of a gunlock that strikes the percussion cap when the trigger is pulled
6. [n]  a heavy metal sphere attached to a flexible wire; used in the hammer throw
7. [n]  the ossicle attached to the eardrum
8. [n]  an athletic competition in which a heavy metal ball that is attached to a flexible wire is hurled as far as possible
9. [v]  beat with or as if with a hammer
10. [v]  of metals

1. \Ham"mer\, n. [OE. hamer, AS. hamer, hamor; akin to D.
   hamer, G. & Dan. hammer, Sw. hammare, Icel. hamarr, hammer,
   crag, and perh. to Gr. ? anvil, Skr. a?man stone.]
   1. An instrument for driving nails, beating metals, and the
      like, consisting of a head, usually of steel or iron,
      fixed crosswise to a handle.
   
            With busy hammers closing rivets up.  --Shak.
   
   2. Something which in firm or action resembles the common
      hammer; as:
      (a) That part of a clock which strikes upon the bell to
          indicate the hour.
      (b) The padded mallet of a piano, which strikes the wires,
          to produce the tones.
      (c) (Anat.) The malleus. See under {Ear}. (Gun.) That part
          of a gunlock which strikes the percussion cap, or
          firing pin; the cock; formerly, however, a piece of
          steel covering the pan of a flintlock musket and
          struck by the flint of the cock to ignite the priming.
      (e) Also, a person of thing that smites or shatters; as,
          St. Augustine was the hammer of heresies.
   
                He met the stern legionaries [of Rome] who had
                been the ``massive iron hammers'' of the whole
                earth.                            --J. H.
                                                  Newman.
   
   {Atmospheric hammer}, a dead-stroke hammer in which the
      spring is formed by confined air.
   
   {Drop hammer}, {Face hammer}, etc. See under {Drop}, {Face},
      etc.
   
   {Hammer fish}. See {Hammerhead}.
   
   {Hammer hardening}, the process of hardening metal by
      hammering it when cold.
   
   {Hammer shell} (Zo["o]l.), any species of {Malleus}, a genus
      of marine bivalve shells, allied to the pearl oysters,
      having the wings narrow and elongated, so as to give them
      a hammer-shaped outline; -- called also {hammer oyster}.
   
   
   {To bring to the hammer}, to put up at auction.
   
   

2. \Ham"mer\, v. t. [imp. & p. p. {Hammered}; p. pr. & vb.
   n. {Hammering}.]
   1. To beat with a hammer; to beat with heavy blows; as, to
      hammer iron.
   
   2. To form or forge with a hammer; to shape by beating.
      ``Hammered money.'' --Dryden.
   
   3. To form in the mind; to shape by hard intellectual labor;
      -- usually with out.
   
            Who was hammering out a penny dialogue. --Jeffry.
   
   

3. \Ham"mer\, v. i.
   1. To be busy forming anything; to labor hard as if shaping
      something with a hammer.
   
            Whereon this month I have hammering.  --Shak.
   
   2. To strike repeated blows, literally or figuratively.
   
            Blood and revenge are hammering in my head. --Shak.
   
   

4. \Ham"mer\, n. (Athletics)
   A spherical weight attached to a flexible handle and hurled
   from a mark or ring. The weight of head and handle is usually
   not less than 16 pounds.
   
   

Commonwealth hackish synonym for bang on.

[jargon file]

(1.) Heb. pattish, used by gold-beaters (Isa. 41:7) and by quarry-men (Jer. 23:29). Metaphorically of Babylon (Jer. 50:23) or Nebuchadnezzar.

(2.) Heb. makabah, a stone-cutter's mallet (1 Kings 6:7), or of any workman (Judg. 4:21; Isa. 44:12).

(3.) Heb. halmuth, a poetical word for a workman's hammer, found only in Judg. 5:26, where it denotes the mallet with which the pins of the tent of the nomad are driven into the ground.

(4.) Heb. mappets, rendered "battle-axe" in Jer. 51:20. This was properly a "mace," which is thus described by Rawlinson: "The Assyrian mace was a short, thin weapon, and must either have been made of a very tough wood or (and this is more probable) of metal. It had an ornamented head, which was sometimes very beautifully modelled, and generally a strap or string at the lower end by which it could be grasped with greater firmness."