What is "underslip"

Usage examples of "underslip".

The bride who was given away by her father, the M'Conifer of the Glands, looked exquisitely charming in a creation carried out in green mercerised silk, moulded on an underslip of gloaming grey, sashed with a yoke of broad emerald and finished with a triple flounce of darkerhued fringe, the scheme being relieved by bretelles and hip insertions of acorn bronze.

Her dress concealed rather than revealed, with layers of underslips, split sleeves, and vests sweeping to her ankles.