1. Having a cutting edge or point that is not sharp
2. Very frank or straightforward
3. To make something less sharp
Remember how when a knife loses its sharp edge, it becomes useless and needs to sharpened again. This means that the knife has become blunt.
1. They tried to blunt their criticism by praising her energy and enthusiasm; this way, their blunts were not so upsetting.
2. He was hit on the head with a blunt instrument.