free-roaming

Short definition from Wiktionary

Verb

1. 1
   present participle and gerund of free-roam
2. 2
   present participle and gerund of free roam

Adjective

1. 1
   Allowing the player to move freely through a virtual world or choose the game narrative and objectives at will; an open world.
2. 2
   Having the ability to move about unconstrained by reins, leashes, fences, cages, barns, and so on.
3. 3
   Not orbiting a gravitational center.