1. . happening, used, or existing inside a…. adj. Whether you’re looking for an indoor play area to keep your kids entertained during inclement weather or you’re looking for birthday party ideas, this list has something for you! The meaning of INDOOR is of or relating to the interior of a building. Or try Evo Rock & Fitness in Portland, both are indoor climbing meccas with resources for adults and kids, beginners and pros. Try Maine’s Salt Pump Climbing in Scarborough. Chicagoland’s suburbs are bursting with options for every age, activity, and price. Maine's largest climbing gym with over 16000 sq feet of climbing. The Family Ice Center in Falmouth is open year-round and offers another variety of active indoor recreation.