Antagonyms Definition

A word that can mean the opposite of itself is an antagonym.

Examples:

bound (bound for Chicago, moving)
bound (tied up, unable to move)

cleave (to cut apart)
cleave (to seal together)

buckle (buckle your pants -- to hold together)
buckle (knees buckled -- to collapse, fall aprt)

citation (award for good behavior)
citation (penalty for bad behavior)

clip (attach to)
clip (cut off from)

cut (get into a line)
cut (get out of a class)

dust (remove dust)
dust (apply dust -- fingerprints)

fast (moving rapidly)
fast (fixed in position)

left (remaining)
left (having gone)

literally (literally)
literally (figuratively)

moot (arguable)
moot (not worthy of argument)

oversight (watchful control)
oversight (something not noticed)

They are also known as contranyms or autoantonyms