As adjectives the difference between gassy and grassy
is that gassy is of a beverage, containing dissolved gas (usually carbon dioxide) while grassy is covered with grass.
gassy
English
Adjective
(er)
Of a beverage, containing dissolved gas (usually carbon dioxide).
Flatulent.
Synonyms
* (of a beverage, containing gas ): fizzy
grassy
English
Adjective
(er)
Covered with grass.
Resembling grass.