1.  shaddock(n = noun.plant) citrus decumana, citrus grandis, citrus maxima, pomelo, pomelo tree, pummelo - southeastern Asian tree producing large fruits resembling grapefruits;
is a kind of citrus, citrus tree
has parts: pomelo, shaddock
is a member of genus citrus

2.  shaddock(n = noun.food) pomelo - large pear-shaped fruit similar to grapefruit but with coarse dry pulp;
is a kind of citrous fruit, citrus, citrus fruit
is a part of citrus decumana, citrus grandis, citrus maxima, pomelo, pomelo tree, pummelo, shaddock

   A tree (Citrus decumana) and its fruit, which is a large species of orange; -- called also forbidden fruit, and pompelmous. [1913 Webster]

shaddock, n. Bot.
1 the largest citrus fruit, with a thick yellow skin and bitter pulp. Also called POMELO.
2 the tree, Citrus grandis, bearing these.

Etymology:
Capt. Shaddock, who introduced it to the W. Indies in the 17th c.