Autoantonyms
An autoantonym is a word which has two meanings which are opposites of each other. It may have several other meanings - only the two contradictory meanings are significant and give an autoantonym its curious "Humpty-Dumpty" quality.

The word cleave - meaning either 'to split asunder' or 'to join together' - is a perfect example of an autoantonym.

DUSTremove dustsprinkle with dust
INFLAMMABLEflammablenot flammable
INHABITABLEhabitablenot habitable
INSCIENTignoranthaving secret or inward knowledge
LEFTremaininggone away
LETto permitto hinder, to prevent
OVERLOOKignoreinspect
PINKa light red coloura greenish-yellow pigment
PRESENTLYnowlater
QUITEcompletely, absolutelyto a partial extent, somewhat
ROCKa sure foundation, anything immovablea swaying or tilting movement
SCREENto conceal from viewto display (a film etc.)
TRIPto move lightly and nimblyto stumble
VAPULATEto flogto be flogged