The Collaborative International Dictionary of English v.0.48:

Botryoid \Bot"ry*oid\, Botryoidal \Bot`ry*oid"al\, a. [Gr. ?
   cluster of grapes + -oid.]
   Having the form of a bunch of grapes; like a cluster of
   grapes, as a mineral presenting an aggregation of small
   spherical or spheroidal prominences; as, botryoidal hematite.

   Syn: botryose.
        [1913 Webster]

WordNet (r) 3.0 (2006):

botryoidal
    adj 1: resembling a cluster of grapes in form [syn: botryoid,
           botryoidal, boytrose]