To bring down, as in extent, amount, or degree; diminish. See Synonyms at decrease. To bring to a humbler, weaker, difficult, or forced state or condition; especially: To gain control of; conquer: "a design to reduce them under absolute despotism\u201d ( Declaration of Independence). To subject to destruction: Enemy bombers reduced the city to rubble. To weaken bodily: was reduced almost to emaciation. To sap the spirit or mental energy of. To compel to desperate acts: The Depression reduced many to begging on street corners. To lower in rank or grade. See Synonyms at demote. To powder or pulverize. To thin (paint) with a solvent. To lower the price of: The store has drastically reduced winter coats. To put in order or arrange systematically. To separate into orderly components by analysis. Chemistry To decrease the valence of (an atom) by adding electrons. Chemistry To remove oxygen from (a compound). Chemistry To add hydrogen to (a compound). Chemistry To change to a metallic state by removing nonmetallic constituents; smelt. Mathematics To simplify the form of (an expression, such as a fraction) without changing the value. Medicine To restore (a fractured or displaced body part) to a normal condition or position. To become diminished. To lose weight, as by dieting. Biology To undergo meiosis.