The Collaborative International Dictionary of English v.0.48:

Bulbil \Bulb"il\, n. [Dim. fr. bulb.]
   1. (Bot.) A small or secondary bulb; hence, now almost
      exclusively: An a["e]rial bulb or deciduous bud, produced
      in the leaf axils, as in the tiger lily, or relpacing the
      flowers, as in some onions, and capable, when separated,
      of propagating the plant; -- called also bulblet and
      brood bud.
      [Webster 1913 Suppl.]

   2. (Anat.) A small hollow bulb, such as an enlargement in a
      small vessel or tube.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

bulbil
    n 1: small bulb or bulb-shaped growth arising from the leaf axil
         or in the place of flowers [syn: bulbil, bulblet]