Definition:
Under a parliamentary system of government, a hung parliament is a legislature in which no political party has an absolute majority of seats. In the case of the United Kingdom, if no party has over 325 seats, then there is a hung parliament.
History:
In 2010, David Cameron's Conservative Party could not reach a majority and so there was a hung parliament with a coalition between the Conservatives and Nick Clegg's Liberal Democrats.
Usage:
"We have a hung parliament this year."
"The Tories could not reach a majority so there will be a hung parliament."