creep up on {v.} 1. To crawl towards; move along near the ground; steal cautiously towards so as not to be seen or noticed. * /The mouse did not see the snake creeping up on it over the rocks./ * /Indians were creeping up on the house through the bushes./ 2. or[sneak up on] To come little by little; arrive slowly and unnoticed. * /The woman's hair was turning gray as age crept up on her./ * /Winter is creeping up on us little by little./ * /The boys didn't notice the darkness creeping up on them while they were playing./ Compare: COME OVER.