If ever – on your travels in the eriador – you would run into a group of dwarves that seem to be shamelessly insulting each other with awfully rude hand gestures… think again… you might be looking at a dwarven sign language called Iglishmêk.

For those not familiar with Iglishmêk (pronounced: [iɡliʃme:k]), it is a gesture language – or sign language. In fact Khuzdul is actually composed of two parts: the aglab, or spoken language, and the iglishmêk, or gesture language.

Iglishmêk is by far the most advanced of the gesture languages of Middle-earth, being the most elaborate and organized system. Dwarves begin learning iglishmêk almost as soon as they begin learning to speak, and use it concurrent with their spoken language. It should also be said that they possess a number of such gesture-codes; for unlike their spoken language, which remain astonishingly uniform and unchanged both in time and in locality, their gesture-codes vary greatly from community to community. And they are differently employed. Not for communication at a distance, for the Dwarves are short-sighted, but for secrecy and the exclusion of strangers.

The component sign-elements of any such code are often so slight and so swift that they can hardly be detected, still less interpreted by uninitiated onlookers. As the Eldar eventually discovered in their dealings with the Naugrim, they can speak with their voices but at the same time by ‘gesture’ convey to their own folk modifications of what is being said. Or they can stand silent considering some proposition, and yet confer among themselves meanwhile.

This ‘gesture-language’, the Dwarves are no more eager to teach than their own tongue. But they understand and respect the disinterested desire for knowledge, and some of the Noldorin loremasters have been allowed to learn enough of both their spoken tongue (Khuzdul) and their iglishmêk to understand their systems.

*War of the Jewels: Quendi and Eldar, p.395

The only known referrence to the actual signs is this:

“I am listening” = slight raising of right-hand forefinger, followed by a similar raising of the left-hand forefinger.
“Listen!” = slight raising of both forefingers simultaneously.*
*J.R.R. Tolkien, “From Quendi and Eldar, Appendix D” (edited by Carl F. Hostetter), in Vinyar Tengwar, Number 39, July 1998, pp. 5, 10