1. to move slowly with the body close to the ground, as a reptile or an insect, or a person on hands and knees.
2. to approach slowly, imperceptibly, or stealthily (often fol. by up): We crept up and peeked over the wall. 
3. to move or advance slowly or gradually: The automobile crept up the hill. Time just seems to creep along on these hot summer days. 
4. to sneak up behind someone or without someone's knowledge (usually fol. by up on): The prisoners crept up on the guard and knocked him out. 
5. to enter or become evident inconspicuously, gradually, or insidiously (often fol. by in or into:) The writer's personal bias occasionally creeps into the account.
6. to move or behave timidly or servilely.
7. to grow along the ground, a wall, etc., as a plant.
8. to advance or develop gradually so as to infringe on or supplant something else: creeping inflation; creeping socialism. 
9. to slip, slide, or shift gradually; become displaced.

the creeps, Informal. a sensation of horror, fear, disgust, etc., suggestive of the feeling induced by something crawling over the skin: That horror movie gave me the creeps.