Contronyms are words (or sometimes short expressions) which have two more or less opposite meanings.
Bolt: To hold together (as in mechanical bolting) or to separate by fleeing.
Garnish: To add to (as with food preparation ) or to take away (as with wages).
Hold up: To support (as in Liberty holding up the torch) or to impede (as in holding up legislation).
Trim: To decorate (as with a Christmas tree) or to remove excess (as with a mustache).
Wind up: To start (as with a clock) or to end (as with a business).