long. movable arm of an aerial device or crane.
Merriam-Webster Online Dictionary
boom (verb)intransitive verb
1.
to make a deep hollow sound
2.
a) to increase in importance, popularity, or esteem
b) to experience a sudden rapid growth and expansion usually with an increase in prices - business was booming
c) to develop rapidly in population and importance - California boomed when gold was discovered there
transitive verb
d) to increase greatly in size or number - the population boomed
1.
to cause to resound - often used with out his voice booms out the lyrics
2.
to cause a rapid growth or increase of - boost
3.
to hit or kick forcefully - boom a punt
1.
a sound or cry - booming often used interjectionally to indicate suddenness then boom, he was fired
2.
a rapid expansion or increase as
a) a general movement in support of a candidate for office
b) rapid settlement and development of a town or district
c) a rapid widespread expansion of economic activity
d) an upsurge in activity, interest, or popularity - a folk music boom
1.
a long spar used to extend the foot of a sail
2.
a) a chain or line of connected floating timbers extended across a river, lake, or harbor (as to obstruct passage or catch floating objects)
b) a temporary floating barrier used to contain an oil spill
3.
a) a long beam projecting from the mast of a derrick to support or guide cargo
b) a long more or less horizontal supporting arm or brace (as for holding a microphone)
4.
a spar or outrigger connecting the tail surfaces and the main supporting structure of an aircraft
boom (Wikipedia)