ride up
verb
- to inch up, such as clothing that moves up the body as one moves
Wiktionary
noun
- The act or process of riding up
verb
- to approach or come near to while riding.
- to move up higher on one's body.
“My jeans always seem to ride up on me in public.”
“The skimpy black underpants had ridden up, and now Chang’s wrinkly old bottom was pointing in their direction.”