From the Italian for "stubborn", an ostinato drives music forward through repetition. Film scores use string ostinatos to build tension; minimalist composers such as Steve Reich and Philip Glass built whole pieces from them.
A bassline that repeats the same riff throughout a song is also an ostinato, as is a repeating synth arpeggio in electronic music.
Using it in a prompt
Ask for "a driving string ostinato" for tension and momentum in trailers, chases and documentaries.