Triveni is a form of Hindi/Urdu poetry initiated by the poet Gulzar.
Unlike sher, a triveni consists of three "hemistichs" (misras).
Rupa & Co. has published his poetry book Triveni.
Sony Music has just released an album Koi Baat Chale which has a few of Gulzar's triveni sung by Jagjit Singh.
A beautiful example of Gulzar's Triveni: The addition of the third line implies that the water drop in the hair is due to a dripping roof and since it creates a visage of such beauty, the poet is unperturbed by it.