Yumnum can describe anything as anything, the way you emphasize it,however, brings out the true meaning.
Kaiti's face is very yumnumalishus. (Different conjugations of the word can be used and in this case it means shes good looking)
I am a yumnum therefore Kaiti is going to marry me because she's reading this. (I don't know what this means im just hoping someone might read this one day and laugh and my insanely crazy sweet definition of my new word)