Groovy is slang, popular in the 50's and 60's, meaning awesome or cool.

Interesting fact! thank you!

People say something like "Thats Groovy" or "Groovy Dude" to say that something is cool, nice, awesome, etc. Also, you never want to say that word because it's totally outdated and people will look at you like a freak if you say it in a sentence. :D Just stick with "Cool" :D