Real Dictionary

boom
If there is a boom in the economy, there is an increase in economic activity, for example in the amount of things that are being bought and sold.

boom in American English 1
to make a deep, hollow, resonant sound
to speak or indicate with such a sound
adjective: caused by or characteristic of a boom
intransitive verb: to make a deep, prolonged, resonant sound
noun: a deep, prolonged, resonant sound
transitive verb: to give forth with a booming sound

boom in American English 2
a spar extending from a mast to hold the bottom of a sail outstretched
noun: any of various more or less horizontal spars or poles for extending the feet of sails, esp. fore-and-aft sails, for handling cargo, suspending mooring lines alongside a vessel, pushing a vessel away from wharves, etc.

boom in American English 3
to increase suddenly in size, importance, activity, etc.; undergo swift, vigorous growth; flourish

boom in British English 1
noun: a deep prolonged resonant sound
verb: to make a deep prolonged resonant sound, as of thunder or artillery fire

boom in British English 2
noun: a spar to which a sail is fastened to control its position relative to the wind

boom in Finance
noun: A financial boom is an increase in economic activity with rapid growth and rising prices.