Jamadar is the word for "captain" in the Taglian language. The term is also used to describe the leader of an independent band of Stranglers. The latter context is the one most commonly used in the Annals of the Black Company during their time in the southern continent (namely, the Books of the South and the Books of Glittering Stone).
Jamadars were "black rumel men" and commanded the unwavering respect of red rumels, yellow rumels, and the bulk of their bands: the grave-diggers and the bone-breakers. The most notorious jamadar in Croaker's lifetime was Narayan Singh.
Another jamadar was Moma Sharrael, whose reputation nearly rivaled that of Narayan. It was Moma who executed the cult's unannounced life-or-death test of Lady during her acceptance into the cult at the Grove of Doom in Dreams of Steel. He attempted to strangle her with his black rumel, but Lady, whose reflexes and actions were supernaturally guided by Kina herself, ripped the weapon from the man's hand and killed him.
The jamadars and their bands were hunted mercilessly by Croaker and Lady throughout Bleak Seasons and She Is the Darkness. When the two returned to the homeworld in Soldiers Live, they resumed the hunt. Although Croaker was certainly not the first person to try to wipe out the Stranglers, he now had the supernatural assistance of the Unknown Shadows, and it seems unlikely that any jamadars would survive.