a light cotton flannel with a short, dense nap.
Origin of outing flannel
An Americanism dating back to 1885–90
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for outing flannel
The outing-flannel night dress completes the outfit and should be the only style of dress worn for the first two weeks.The Mother and Her Child|William S. Sadler