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A substance added to another substance to modify, dilute, or add to it: meatloaf that contained oatmeal as an extender.
1. a person or thing that extends
2. (Chemical Engineering) a substance, such as French chalk or china clay, added to paints to give them body and decrease their rate of settlement
3. (Chemical Engineering) a substance added to glues and resins to dilute them or to modify their viscosity
4. (Chemistry) a substance added to elastomers to assist the plasticizer
5. (Printing, Lithography & Bookbinding) printing the part of certain lower-case letters that extends either above (the ascender) or below (the descender) the body of the letter
a substance added to another substance, as to paint or food, to increase its volume or bulk.