The phrase "touches off" typically means to initiate or spark something, but there are several antonyms that convey the opposite meaning. One antonym for "touches off" is "stifles," which means to suppress or extinguish. Another antonym is "quashes," which means to squash, crush, or put an end to. Additionally, "quenches" is another antonym for "touches off," which suggests putting out a fire, e.g., extinguishing one's anger or desire. Other antonyms include "suppresses," "restrains," "conceals," and "contain," indicating that the opposite of igniting or setting off something is to smother or restrain it.