"Unlimited sprint" means having the ability to run or move quickly without any restrictions or limitations on how long you can do it for. Full definition
Whereas Halo 4 regretfully embraced sprint, Halo 5: Guardians addresses sprint perfectly: by allowing unlimited sprint for those that want it, but doing so means that your shields will not recharge for an extended period of time. (gamingtrend.com)
Rockstar have considered all multiplayer gameplay issues - such as time and ammo limits - and they have countered these problems through such features as unlimited sprint and regular weapon pickups. (gtalibertycitystories.net)
The player will also unlock perks, which modify certain gameplay elements like unlimited sprint and increased bullet damage. (propcgame.com)