The Collaborative International Dictionary
Shirt waist
shirtwaist \shirtwaist\, Shirt waist \Shirt waist\ [shirt + waist; see waist[3], n.]
A woman's blouse resembling a men's shirt in cut and style; -- in England called a blouse.
a type of woman's dress with a bodice tailored like a shirt; -- also called shirt dress, shirtwaist dress, and shirtwaister.
--[RHUD]
Wiktionary
shirt waist
n. (alternative spelling of shirtwaist English)