(adj.) Describes something so revolting in nature that the words gross or nasty alone would not be enough.
ex1) What happened was so grossty that I vomited my guts all over the pavement.
ex2) "That shiz is grossty yo."
ex3) The doctor removed grossty fluids from Eddies injured knee.
A combination of the words "gross" and "nasty", it is an adjective that goes above and beyond both terms. Can be applied to the hygene of an individual, food products, or any other situation where such a description is necessary.
Very similar to how "fugly" describes something exceedingly unattractive, using a combination of two words.
Jake: When I came in just now, I smelled the nastiest stench as I walked into our apartment. It was like a combination of Febreeze, ramen noodles, some other food and dust.
Jared: Let me smell it to see if I can find out what it is.
Jared: Oh man, that is just grossty.