pacing vs rubato

pacing and rubato both are nouns.

Word	Noun	Adjective	Verb	Adverb
pacing	Yes	No	No	No
rubato	Yes	No	No	No

As nouns, rubato is a hyponym of pacing; that is, rubato is a word with a more specific, narrower meaning than pacing:

Other hyponyms of pacing include accelerando, allegretto, allegro, andante, meno mosso.

pacing (noun)	rubato (noun)
walking with slow regular strides	a flexible tempo; not strictly on the beat
(music) the speed at which a composition is to be played