the ratio, in an elastic body under longitudinal stress, of the transverse strain to the longitudinal strain.
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British Dictionary definitions for Poisson's ratio
a measure of the elastic properties of a material expressed as the ratio of the fractional contraction in breadth to the fractional increase in length when the material is stretched: Symbol: μ, ν
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012