IPA: /ˈɡæsiər/
KK: /ˈgæs.i.ɚ/
Having more gas than something else; used to describe something that produces or contains a lot of gas.
The gassier of the two options was not suitable for the experiment.
Comparative: gassier
Superlative: gassiest
The word 'gassier' is derived from 'gas' (from French 'gaz', meaning vapor or gas) and the suffix '-ier' (meaning one who or that which). Therefore, 'gassier' refers to something that is more gaseous or has the quality of gas.
Think of 'gas' as a vapor and remember that 'gassier' means something that is more like gas.