IPA: /ˈɡroʊsɪst/
KK: /groʊsɪst/
The most unpleasant or disgusting; the highest degree of something that is considered offensive or distasteful.
That was the grossest thing I've ever seen!
Comparative: grosser
Superlative: grossest
Grossest → It is formed from "gross" (from Old French *gros*, meaning thick or large) and the superlative suffix "-est" (meaning most). The word "grossest" means the most thick or large, often used to describe something that is unpleasant or offensive in a strong way.
Think of something that is the 'most' ('-est') 'large' or 'thick' ('gross') — that's why grossest refers to something that is extremely unpleasant.