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a. A window sash that opens outward by means of hinges.
b. A window with such sashes.
2. A case or covering.
[Middle English, a hollow molding, possibly from Middle English case, chest, frame; see case2.]
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.