spike somebody's guns

spike (one's) guns

To ruin one's plans or prevent one's success. The phrase refers to the former military practice of inserting spikes into enemy guns to prevent them from firing. I'm afraid the rain has spiked our guns. We cannot hold the rally as planned.
See also: gun, spike

spike somebody’s ˈguns

(British English) spoil somebody’s plans because you do not want them to succeed: She was jealous of David’s progress in the company, so she spiked his guns by telling the boss that David had a drinking problem.This refers to pushing a metal spike (= a thin object with a sharp point) into the enemy’s gun or cannon so that it cannot be fired.
See also: gun, spike