WordWeb Online

1. Be the essential element
   "The proposal boils down to a compromise";
   - reduce, come down
    
2. (cooking) be cooked until very little liquid is left
   "The sauce should boil down to one cup";
   - reduce, decoct [archaic], concentrate
    
3. (cooking) cook until very little liquid is left
   "The cook boiled down the sauce by boiling it for a long time";
   - reduce, concentrate

Derived forms: boiled down, boiling down, boils down

Type of: become, decrease, diminish, fall, lessen, minify, turn