Definition from Wiktionary, the free dictionary
guay m, f (plural guais) guay (invariable)
- This adjective is most often treated as invariable, with the form guay being used regardless of gender or number; however, the plural form guais is also often found. Hence, “They're very cool” may be expressed either as son muy guay or as son muy guays.
- Often expanded to guay de Paraguay.