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tr.v. de·rat·ed, de·rat·ing, de·rates
1. To lower the rating of (a device), especially because of a deterioration in efficiency or quality.
2. To lower the financial rating of (a corporation, for example).
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.
(Government, Politics & Diplomacy) (tr) Brit to assess the value of (some types of property, such as agricultural land) at a lower rate than others for local taxation
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
Past participle: derated
Collins English Verb Tables © HarperCollins Publishers 2011