noun
to start before preparations are complete, so that the effect or result is not as it should be
数据来源：WordNet
n.
go off at half-cock
(BrE informal)没准备好就开始干，操之过急（而效果或结果不好） to start before preparations are complete, so that the effect or result is not as it should be
half-cockhalf-cockhalf-cock