"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.
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.
The player will also unlock perks, which modify certain gameplay elements
like unlimited sprint and increased bullet damage.
While including this interesting balancing technique is a welcome change to the series,
unlimited sprint makes Halo 5: Guardians blisteringly fast and feel far too much like the Call of Duty series.
In this title, they ditched the health auto refill and
unlimited sprint for a more realistic feeling.
This new character class boasts
an unlimited sprint and the abilities to call in artillery strikes and deploy mobile respawn points for friendlies.
Features like double jumping and
unlimited sprint are also gone.
Because of this, and to maintain fast gameplay, Rockstar have added «
unlimited sprint» which means you never get tired whilst running.
One other highlight of the new changes is that all players now have
unlimited sprint, however, your overall speed will be slower.