ex·pand (?k-sp?nd?)v. ex·pand·ed, ex·pand·ing, ex·pands v.tr.1. To increase the size, volume, quantity, or scope of; enlarge: expanded her store by adding a second room. See Synonyms at increase.2. To express at length or in detail; enlarge on: expanded his remarks afterward.3. To open (something) up or out; spread out: The bird expanded its wings and flew off.4. Mathematics To write (a quantity) as a sum of terms in an extended form.v.intr.1. To become greater in size, volume, quantity, or scope: Air expands when heated. This critic’s influence is expanding.2. To speak or write at length or in detail: expand on a favorite topic.3. To open up or out; unfold: The chair expands to form a daybed.[Middle English expanden, to spread out, from Latin expandere : ex-, ex- + pandere, to spread; see pet?- in Indo-European roots.]ex·pand?a·ble adj.ex·pand?er n.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.expander (?k?spænd?) n1. a device for exercising and developing the muscles of the body: a chest expander. 2. (Electronics) an electronic device for increasing the variations in signal amplitude in a transmission system according to a specified law. Compare compressor5, companderCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014