a blouse designed to be worn outside the waistband of a skirt or a pair of slacks.
Origin of overblouse
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
a blouse designed to be worn not tucked into trousers or a skirt but to fit loosely over the waist or hips
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