Sentence:  What Stewart called a “langtailie coat” spread out behind him like streamers in a breeze, a “biled” collar had, in the same gentleman's terse language, “burst its moorings” and projected in two miniature wings at the back of his ears, and a shirt that had once been white, <WSD>bosomed</WSD> out expansively through an open vest. 
Meaning of the word marked with <WSD> tags:  To belly; to billow, swell or bulge.