Hola Isabel: "Cool" as synonim of great/fantastic (That car is so cool!) is kind of an idiomatic expression, so it's different in every Spanish speaking country. In a general sense, you could say "genial" in any country. Some "country-specific" words are "chévere, guay, groso,bacán,.....and many many others: Bye!

Hola Isabel, en el centro de México decimos "Chido" para referirnos a algo "cool"

well, in colombia there is a very popular word that has the same meaning for cool, the word is "vacano"

Hola Isabel, *guay (español de España) ¡ala, qué guay! , ¡ala, cómo mola! = Hey, that's really cool! *padre (español de México) = enorme *copado *macanudo ( estupendo)

No es tan sencillo! Como adjetivo puede ser "guay", "genial", "frio", "fresco", "tranquilo" o "calma"; como verbo puede ser "enfriar" o "refrigerar". Eso depende totalmente del contexto.