In religious festivals of Gaudiya Vaishnavism Hari
Bol is called out meaning: "Sing the name of Hari" or "Call out (or chant) the name of Hari". (Hari being the name for Krsna and Visnu)
From a more direct hindi translation:
Bol = to speak, Hari = (a)
god
It is used in many Hindi devotional songs.
