Definition: foursquare

A social networking site that serves as a mobile friend finder and loyalty card service. Founded in 2008 by Dennis Crowley and Naveen Selvadurai, foursquare members "check in" via smartphone when visiting a venue and share their location with foursquare friends, Facebook and X/Twitter. Members can also leave tips about a place to help future visitors.

Points, Discounts, Badges and Mayorships
When users check in, they get points to compare themselves with other members. After checking in some number of times, sponsoring companies offer members discounts and freebies and may surprise them with achievement badges.

If a foursquare member checks into a venue more than anyone else in the past 60 days, that person becomes "mayor" of that venue. Members getting close to mayor status are notified ahead of time.