The Collaborative International Dictionary of English v.0.48:
Breastpin \Breast"pin`\ (br[e^]st"p[i^]n`), n. A pin worn on the breast for a fastening, or for ornament; a brooch. [1913 Webster]WordNet (r) 3.0 (2006):
breastpin n 1: a decorative pin worn by women [syn: brooch, broach, breastpin]