This word was looked up more than any other during the first week of the FIFA World Cup, which began on June 11, 2010.
South African fans brought their favorite noisemaker, the vuvuzela, to the World Cup matches bringing much attention to the horn itself and its effect on the game.
As Reuters reported,
"If you cannot beat the vuvuzela, the Swiss squad decided, you might as well embrace the cacophony which is blighting Africa's first World Cup for many fans and players. Coach Ottmar Hitzfeld ... decided to encourage fans to blow the ubiquitous trumpets at an extra public training session to give his side a taste of dins to come when they play their first match." David Clarke, June 15, 2010
Cacophony means "harsh sound." It's rooted in the ancient Greek word kakaphōnia, which comes from kak ("bad") + phōnia ("sound").
Side Note: Vuvuzela does not yet appear in an official Merriam-Webster dictionary, but soon after the World Cup started, it became part of our online Open Dictionary:
vuvuzela (noun) : a long horn consisting of a straight tube made of aluminum or plastic that emits a loud monotone and
that is often blown at sporting events as a rallying device