ride up

ride up

1. To approach someone or something on horseback. The sheriff rode up to see what the two suspicious characters were up to.
2. To gradually move or slide upward on one's body, especially when becoming wedged some place or bunched together. My underwear keeps riding up and giving me a wedgie! I really love this dress, but it keeps riding up on me whenever I stand up.
See also: ride, up
Farlex Dictionary of Idioms.

ride up

 (on someone)
1. Lit. [for someone on a horse] to approach someone, riding. I rode up on him and frightened him. I guess I was in the house when you rode up.
2. Fig. [for clothing, especially underpants] to keep moving higher on one's body. I don't like it when my pants ride up on me. I hate it when my underpants ride up.
See also: ride, up
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

ride up

Gradually move upward from a normal position, as in This skirt is too tight and it constantly rides up. [Mid-1800s]
See also: ride, up
The American Heritage® Dictionary of Idioms by Christine Ammer.

ride up

v.
To slide upward across the surface of something and become bunched together. Used especially of fabric or clothing: My sleeves always ride up my arms when I wear this coat. I don't like this brand of underwear—they ride up and are really uncomfortable.
See also: ride, up
The American Heritage® Dictionary of Phrasal Verbs.
See also:
  • have a scrape
  • on horseback
  • be on the watch
  • be on the watch (for someone or something)
  • get wise to (someone or something)
  • give someone his/her head, to
  • How do ye do?
  • be wise to (someone or something)
  • be/get wise to somebody/something
  • cat around