armored mud ball
armored mud ball[′är·mərd ′məd ‚bȯl]
A large (0.4-20 inches or 1-50 centimeters in diameter) subspherical mass of silt or clay coated with coarse sand and fine gravel. Also known as pudding ball.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.