a long pole or spar, run out for the purpose of extending the bottom of a particular sail; as, the jib boom, the studding-sail boom, etc.-a long spar or beam, projecting from the mast of a derrick, from the outer end of which the body to be lifted is suspended.-a pole with a conspicuous top, set up to mark the channel in a river or harbor.-a strong chain cable, or line of spars bound together, extended across a river or the mouth of a harbor, to obstruct navigation or passage.-a line of connected floating timbers stretched across a river, or inclosing an area of water, to keep saw logs, etc., from floating away.-to extend, or push, with a boom or pole; as, to boom out a sail; to boom off a boat.-to cry with a hollow note; to make a hollow sound, as the bittern, and some insects.-to make a hollow sound, as of waves or cannon.-to rush with violence and noise, as a ship under a press of sail, before a free wind.-to have a rapid growth in market value or in popular favor; to go on rushingly.-a hollow roar, as of waves or cannon; also, the hollow cry of the bittern; a booming.-a strong and extensive advance, with more or less noisy excitement; -- applied colloquially or humorously to market prices, the demand for stocks or commodities and to political chances of aspirants to office; as, a boom in the stock market; a boom in coffee.-to cause to advance rapidly in price; as, to boom railroad or mining shares; to create a "boom" for; as to boom mr. c. for senator.