Definition of one up
: being in a position of advantage —usually used with on
First Known Use of one up
ONE UP Defined for English Language Learners
Definition of one up for English Language Learners
: having an advantage over someone : in a position that is better than someone else's position
Seen and Heard
What made you want to look up one up? Please tell us where you read or heard it (including the quote, if possible).