gigacycle per second vs rate

gigacycle per second and rate both are nouns.

Word	Noun	Adjective	Verb	Adverb
gigacycle per second	Yes	No	No	No
rate	Yes	No	Yes	No

As nouns, rate is a hypernym of gigacycle per second; that is, rate is a word with a broader meaning than gigacycle per second:

gigacycle per second (noun)	rate (noun)
1,000,000,000 periods per second	the relative speed of progress or change
	amount of a charge or payment relative to some basis
	a quantity or amount or measure considered as a proportion of another quantity or amount or measure
	a magnitude or frequency relative to a time unit

gigacycle per second (verb)	rate (verb)
	assign a rank or rating to
	estimate the value of
	be worthy of or have a certain rating