IPA: /ˈɡæsiɪst/
KK: /ˈɡæs.i.ɪst/
Having the most gas; characterized by a high amount of gas.
The gassiest planet in our solar system is Jupiter.
Comparative: gassier
Superlative: gassiest
Gassiest → It is formed from "gas" (from Latin *gasium*, meaning a state of matter that is neither solid nor liquid) and the suffix "-iest" (meaning most). The word "gassiest" means having the most gas or being in the state of gas to the highest degree.
Think of 'gas' as a state of matter and remember that 'gassiest' means having the most of that state.