The Language Translator is a program installed in some Predators' bio-masks that allows a Hunter to understand other species' communication(s)/language(s).
Alien vs. Predator
Like all Yautja technology, the Language Translator is far from anything known to humans. From the Predator's view, the Translator shows the sound waves of the speech and translates it to the Yautja language. Three of the Predator protagonists in the 2004 film Alien vs. Predator, Scar, Celtic, and Chopper, all have the translator installed in their masks. While they stalked the humans, it gave them the advantage of knowing the team's plans. Scar, however, used it while he worked with the sole survivor of the expedition team, Alexa Woods, to understand what she had said to him.
Ultimate Predator uses language translator to The Loonies and Project Stargazer personnel to mock them, then stating them its intention to claim Rory for a trophy.