Etymology 1 
From Middle English crepen, from Old English crēopan (“to creep, crawl”), from Proto-Germanic *kreupaną (“to twist, creep”), from Proto-Indo-European *ger- (“to turn, wind”). Cognate with West Frisian krippe, krûpe, Eastern Frisian crjippa (“to creep”), Low German krepen, krupen, Dutch kruipen (“to creep, crawl”), Middle High German kriefen (“to creep”), Danish krybe (“to creep”), Norwegian krype (“to creep”), Swedish krypa (“to creep, crawl”), Icelandic krjúpa (“to stoop”).
- (intransitive) To move slowly with the abdomen close to the ground.
- Lizards and snakes crept over the ground.
- (intransitive) Of plants, to grow across a surface rather than upwards.
- (intransitive) To move slowly and quietly in a particular direction.
- He tried to creep past the guard without being seen.
- (intransitive) To make small gradual changes, usually in a particular direction.
- Prices have been creeping up all year.
- (move slowly with the abdomen close to the ground): crawl
- (grow across a surface rather than upwards):
- (move slowly and quietly in a particular direction):
- (make small gradual changes):
Derived terms 
Etymology 2 
From the above verb.
creep (plural creeps)
- The movement of something that creeps (like worms or snails)
- A relatively small gradual change, variation or deviation (from a planned value) in a measure.
- A slight displacement of an object: the slight movement of something
- The gradual expansion or proliferation of something beyond its original goals or boundaries, considered negatively.
- Christmas creep. Feature creep. Instruction creep. Mission creep
- (publishing) In sewn books, the tendency of pages on the inside of a quire to stand out farther than those on the outside of it.
- (materials science) An increase in strain with time; the gradual flow or deformation of a material under stress.
- (geology) The imperceptible downslope movement of surface rock.
- (informal, pejorative) An annoying irritating person
- (informal, pejorative) A frightening and/or disconcerting person, especially one who gives the speaker chills or who induces psychosomatic facial itching.
- Stop following me, you creep!
- (agriculture) A barrier with small openings used to keep large animals out while allowing smaller animals to pass through.