a layer of material or cushioning between the outsole and the insole of a shoe.
Origin of midsole
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
a layer between the inner and the outer sole of a shoe, contoured for absorbing shock
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