Definition of "one up"

one up

verb
third-person singular simple present one ups, present participle one upping, simple past and past participle one upped
1. (idiomatic) To outdo, to perform something slightly better than a competitor's prior effort.
noun
plural one ups
1. (especially in phrases like get one up on someone) An advantage over someone.
2. (video games) Alternative spelling of 1-up (“extra life”)