WordNet sense 1 (put down by force or intimidation):

quash, repress, subdue, subjugate, repress, keep down

WordNet sense 2 (cut down on; make a reduction in):

cut, trim, bring down, cut back, cut down, trim back, trim down

WordNet sense 3 (reduce in scope while retaining essential elements):

abbreviate, abridge, contract, foreshorten, shorten, contract

WordNet sense 4 (reduce in size; reduce physically):

shrink

WordNet sense 5 (make smaller):

scale down

WordNet sense 6 (to remove oxygen from a compound, or cause to react with hydrogen or form a hydride, or to undergo an increase in the number of electrons):

deoxidise, deoxidize

WordNet sense 7 (be the essential element):

boil down, come down

WordNet sense 8 (be cooked until very little liquid is left):

concentrate, decoct

WordNet sense 9 (narrow or limit):

tighten

WordNet sense 10 (lessen the strength or flavor of a solution or mixture):

dilute, thin, thin out

WordNet sense 11 (take off weight):

slenderize, slim, lose weight, melt off, slim down