A creeper is a plant that grows very low to the ground or close to a wall or fence. Many types of ivy and other vines are creepers.
You might want to create some privacy in your yard by planting a creeper beside your chain link fence — it will creep along the ground and up the fence itself, forming a leafy barrier between you and your neighbors. Other kinds of creepers are small birds that tend to stay on the ground or creep around in trees and bushes. You can also use this word informally to mean someone who acts in a creepy, or inappropriate, way.