fizzle yield
n.— «Moreover the institute paper points out that with a relatively crude gun-type device, there is a good chance of a problem known as pre-detonation, where the nuclear chain reaction starts too soon, resulting in what is called a “fizzle yield”an explosion equivalent to just a few thousands pounds of dynamite, as opposed to the hundred thousand pounds of a successful 10 kiloton nuke.» —“Analysis: No real terror A-bomb threat” by Shaun Waterman United Press International Nov. 5, 2006. (source: Double-Tongued Dictionary)