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pillow structure[′pil·ō ‚strək·chər]
A primary sedimentary structure that resembles a pillow in size and shape. Also known as mammillary structure.
A pillow-shaped structure visible in some extrusive lavas attributed to the congealment of lava under water.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.