Geonosian was the language of the Geonosian species native to Geonosis. It consisted of click consonants, possible through the dual-mandibles of Geonosians—one moving vertically, and a second, internal set moving horizontally.
Aristocrat Geonosians were also able to understand Basic fluently, unlike the lesser castes. It is unknown if they were all physically unable to speak Basic (much like Wookiees), or if they simply preferred their own language. The QueenKarina was known to be capable of speaking Basic. An off-world Geonosian, Tookra could also speak Basic[1].
The language was mostly spoken by Geonosians, but there have been instances of offworlders understanding Geonosian without the immediate need of a translator- Count Dooku[2], Shu Mai[3], Senator Padmé Amidala and Ysanne Isard are notable examples. Marmio Mio also learned the language while on the planet.[4]
It should be noted, however, that the human voice-chords were apparently capable of reproducing the Geonosian sounds. Infected clones were able to reproduce the sound fairly simply and authentically. [5]
In a Hyperspace online chat, Matthew Wood said that the sound of the Geonosians was one of the weirdest he had ever recorded for a Star Wars movie. It consisted of a penguin mating call as well as fruit bats fighting over a banana.