A murki is a fast, feather-light ornament: a small, rapid turn of two or three notes that flits around the main note without the weight of a gamak. It adds sweetness and agility to a phrase.
Murkis are especially characteristic of thumri, ghazal and other expressive, lighter genres, where delicacy matters more than power. They are close cousins of the khatka, and a singer's murkis are often a signature of personal style.
Though small, murkis are difficult to execute cleanly at speed, and tasteful murki-work is a mark of refinement.