touch off vs spark

touch off is not a noun while spark is a noun.

Word	Noun	Adjective	Verb	Adverb
touch off	No	No	Yes	No
spark	Yes	No	Yes	No

As verbs, touch off and spark are synonyms defined as:

Other synonyms of touch off include activate, actuate, set off, spark off, trigger, trigger off, trip.

touch off (noun)	spark (noun)
	merriment expressed by a brightness or gleam or animation of countenance
	a momentary flash of light
	a small fragment of a burning substance thrown out by burning material or by friction
	electrical conduction through a gas in an applied electric field
	a small but noticeable trace of some quality that might become stronger

touch off (verb)	spark (verb)
put in motion or move to act	put in motion or move to act
	emit or produce sparks