A creeper is a plant that grows along the ground or climbs up surfaces by spreading out rather than growing tall and straight. A creeper typically sprawls across whatever surface it finds. Ivy is a common creeper that spreads across walls and fences. Strawberry plants send out creepers (called runners) that stretch along the ground and form new plants. In gardens, creepers can be helpful ground cover, filling in bare spots and preventing weeds, but they can also take over if you're not careful.

The word also means someone or something that moves quietly and secretly, trying not to be noticed. You might creep down the hallway at night, stepping softly so you don't wake anyone. In this sense, a creeper is someone or something that creeps: a cat might be a skilled creeper as it stalks a toy mouse.

People sometimes use “creeper” to describe someone who makes others uncomfortable by acting strangely or intrusively, but that's informal slang rather than the word's main definition.