—n. 1. the hole, slit, or loop through which a button is passed and by which it is secured.
2. Chiefly Brit.a boutonniere.
3. Surg.a short, straight incision through the wall of a cavity or a canal.
—v.t. 1. to sew with a buttonhole stitch.
2. to make buttonholes in.
3. to hold by the buttonhole or otherwise abruptly detain (someone) in conversation: The reporter tried to buttonhole the mayor for a statement on the bus strike.