From The Collaborative International Dictionary of English v.0.48:
yummy \yum"my\ (y[u^]m"m[y^]), adj.
Very pleasing or attractive; especially, pleasing to the
taste; delicious; scrumptious. [colloq.]
Syn: delectable, delicious, luscious, pleasant-tasting,
scrumptious, toothsome.
[PJC + WordNet 1.5]