something that puts a stop to something or defeats something
Barbara left London on the cusp of a change that dealt a killer blow to Mayfair glamour
as the dream of the young.
The pace slackened in the second half, but it was Morientes who delivered the killer
blow in the 72nd minute.
The United manager, Sir Alex Ferguson, has described the loss of Darren Fletcher as
a 'killer blow' to Scotland's World Cup hopes.
Collins English Dictionary. Copyright © HarperCollins Publishers