What does "hammer" mean?

Hammer: 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 (Zoöl.), 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.