WordWeb Online

1. Cause to seem less serious; play down
   "Don't belittle his influence";
   - minimize, denigrate, derogate, minimise [Brit]
    
2. Express a negative opinion of
   "She belittled her student's efforts";
   - disparage, pick at
    
3. Lessen the authority, dignity, or reputation of
   "don't belittle your colleagues";
   - diminish

Derived forms: belittles, belittled, belittling

Type of: criticise [Brit], criticize, damn, decrease, knock, lessen, minify, pick apart