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]

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "buttonhole":
   accost, address, apostrophize, appeal to, apply pressure, approach,
   beset, besiege, bespeak, blandish, bore, bore stiff, bore to death,
   bore to distraction, bore to tears, boutonniere, bug, cajole,
   call to, coax, corner, corsage, detain, dun, exert pressure, greet,
   hail, halloo, importune, invoke, nag, nag at, pester, plague, ply,
   press, pressure, push, salute, send to sleep, speak, speak fair,
   speak to, take aside, talk to, tease, urge, waylay, wheedle,
   work on