to meet sb or find sth by chance; to dash over to a nearby place, often to fetch something
Oxford43% of films
to meet sb or find sth by chance
you didn't run across Ciara nowhere, did you?
Editorial29% of films
to dash over to a nearby place, often to fetch something
But I'll run across, get us something to eat.
Definitions from the Oxford Advanced Learner's Dictionary, 9th edition