The Collaborative International Dictionary of English v.0.48:

shirtwaist \shirtwaist\, Shirt waist \Shirt waist\ [shirt +
   waist; see waist[3], n.]
   1. A woman's blouse resembling a men's shirt in cut and
      style; -- in England called a blouse.
      [Webster 1913 Suppl. +PJC]

   2. a type of woman's dress with a bodice tailored like a
      shirt; -- also called shirt dress, shirtwaist dress,
      and shirtwaister. --[RHUD]
      [PJC]

WordNet (r) 3.0 (2006):

shirtwaister
    n 1: a blouse with buttons down the front; "in Britain they call
         a shirtwaist a shirtwaister" [syn: shirtwaist,
         shirtwaister]