(Just to make it even worse you say it GYOOlossity.)
It means greed or gluttony.
Now, obviously gluttony in particular is a greatly satisfying word of enormous clattering charm and anyone in their right mind will much prefer it.
Frank Richard's Billy Bunter, illustrated by C. H. Chapman
I suppose that there's something swollen and indigestible about the word gulosity that does echo its meaning.
It certainly echoes the state of the ego of any user, anyway.
Word Not To Use Today: gulosity. This word comes from the Latin gulōsitās, from gula, which means gullet.