The Collaborative International Dictionary of English v.0.48:

Aroid \A"roid\, Aroideous \A*roid"e*ous\, a. [Arum + -oid.]
   (Bot.)
   Belonging to, or resembling, the Arum family of plants
   (Araceae).

   Syn: araceous
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Aroid \Ar"oid\, n. [Arum + -oid.] (Bot.)
   Any plant of the Arum family (Arace[ae]); -- have small
   flowers massed on a spadix surrounded by a large spathe.

   Syn: arum
        [Webster 1913 Suppl. + WordNet 1.5]

WordNet (r) 3.0 (2006):

aroid
    adj 1: relating to a plant of the family Araceae [syn: aroid,
           araceous]
    n 1: any plant of the family Araceae; have small flowers massed
         on a spadix surrounded by a large spathe [syn: arum,
         aroid]