1. To lessen
2. To make smaller; SYN. scale down.
3. To make less complex; SYN. simplify.
4. To narrow or limit; SYN. tighten.
5. To lower in grade or rank; force somebody into an unpleasant situation.
6. To cut down on; make a reduction in; SYN. cut down, cut back, trim, trim down, trim back, cut, bring down.
7. To bring to humbler or weaker state or condition
8. To simplify the form of a mathematical equation of expression by substituting one term for another.
9. To take off weight; SYN. melt off, lose weight, slim, slenderize, thin, slim down.
10. To reposition back to its normal site, as of a broken bone, in surgery.
11. To undergo meiosis
12. To cook until very little liquid is left, as of sauces; SYN. boil down, concentrate.

In a graphical user interface, to decrease the size of a window. A user can reduce a window either by clicking the appropriate button in the title bar or by clicking the mouse on the border of the window and dragging the border toward the middle of the window. See also maximize, minimize.