WordNet sense 1 (a person who takes a position in the political center):

centrist, moderationist

WordNet sense 2 (lessen the intensity of; temper; hold in restraint; hold or keep within limits):

check, contain, control, curb, hold, hold in

WordNet sense 3 (marked by avoidance of extravagance or extremes):

restrained

WordNet sense 4 (not extreme in behavior):

temperate

WordNet sense 5 (not large but sufficient in size or amount):

modest

WordNet sense 6 (not excessive):

limited

WordNet sense 7 (neither too great nor too little):

indifferent

WordNet sense 8 (not excessive or extreme):

fair, reasonable

WordNet sense 9 (avoiding excess):

cautious, conservative

WordNet sense 10 (around the middle of a scale of evaluation of physical measures):

intermediate, medium, intermediate

WordNet sense 11 (moderate in type or degree or effect or force; far from extreme):

mild

WordNet sense 12 (make less severe or harsh):

mince, soften

WordNet sense 13 (make less strong or intense; soften):

tame, tone down

WordNet sense 14 (preside over):

chair, lead, lead, lead

WordNet sense 15 (restrain or temper):

chasten, temper