A manipulative practice in which a trader enters a large sell order or a series of sell orders intending to force a security price below its normal equilibrium level. It is a type of price manipulation that is designed to obstruct price competition in a market in order to artificially produce low prices.

Hammering could also refer to an announcement on the London Stock Exchange (LSE) that a broker is unable to fulfill his obligations towards other participants. The exchange used to do this by sounding three hammer blows followed by the announcement of the broker’s identity.