shorten - make shorter than originally intended; reduce or retrench in length or duration; "He shortened his trip due to illness"

quench - reduce the degree of (luminescence or phosphorescence) in (excited molecules or a material) by adding a suitable substance

cut - have a reducing effect; "This cuts into my earnings"

retrench - make a reduction, as in one's workforce; "The company had to retrench"

slash - cut drastically; "Prices were slashed"

thin out - make sparse; "thin out the young plants"

thin - make thin or thinner; "Thin the solution"

minify, decrease, lessen - make smaller; "He decreased his staff"

detract, take away - take away a part from; diminish; "His bad manners detract from his good character"

deflate - reduce or cut back the amount or availability of, creating a decline in value or prices; "deflate the currency"

inflate - increase the amount or availability of, creating a rise in value; "inflate the currency"

knock off, shave - cut the price of