General synonyms:
* Crush
* Grind
* Reduce to powder
* Comminute
* Mince
* Shred
* Demolish
* Destroy
* Shatter
* Annihilate
More specific synonyms:
* Mill (for grinding grain)
* Masticate (for chewing)
* Triturate (for grinding in a mortar)
* Disintegrate (for breaking down into small particles)
The best synonym will depend on the specific meaning you want to convey. For example, if you are talking about crushing rocks, "pulverize" is a good choice. If you are talking about destroying something completely, "annihilate" might be a better option.