The Collaborative International Dictionary of English v.0.48:

Buttonhole \But"ton*hole`\, n.
   The hole or loop in which a button is caught.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Buttonhole \But"ton*hole`\, v. t.
   To hold at the button or buttonhole; to detain in
   conversation to weariness; to bore; as, he buttonholed me a
   quarter of an hour.
   [1913 Webster]

WordNet (r) 3.0 (2006):

buttonhole
    n 1: a hole through which buttons are pushed [syn: buttonhole,
         button hole]
    v 1: detain in conversation by or as if by holding on to the
         outer garments of; as for political or economic favors
         [syn: lobby, buttonhole]