meetup

I was just trying to find out what "meetup" means (in "the meetup was fun.."), but no dictionary has it. Googling it shows this "word" seems to originate from some popular site (meetup dot com) plus million results when searching for "meetup", "meetups" etc. Does that mean "meetup" is already a common word that I can use in my everyday life and not sound weird, especially to people not familiar with Internet? (I'm a non-native speaker)