The Universal Translator, also simply called the UT, was a device used by the boys from the Dwarf to translate any language, or even thought forms, directly into the English language.

They didn't often need it, as Kryten had studied almost every language or dialect known to man, for example Kryten was able to talk the language of the Kinitawowi GELFs. ("Emohawk") They were also able to understand the backwards English language of htraE through Kryten reversing it. ("Backwards")

One Universal Translator was present aboard Starbug, and with which the crew used to communicate with the intelligent virus Epideme. ("Epideme")

Trivia

• The UT was presumably the device used to translate the GELF Space Icon in an earlier episode.
• The existence of the Universal Translator may explain some apparent plot inconsistencies in the show. For example, how they were able to have conversations with people in the distant past, who apparently speak perfect English ("Lemons"), or would explain how Lister was able to play poker with the BEGGs before the BEGGs revealed that they could actually speak English. ("Entangled")
• Arnold Rimmer's desperate, repeated yet completely failed attempts to learn Esperanto - the semi-official language of the JMC - could have done with some help from the UT ("Kryten"). However it is unlikely Rimmer would have been allowed to take a UT into his astro-navigation exams.

Behind the Scenes

• It is likely the Universal Translator is based on a device of the same name that features in the Star Trek universe (where it serves the same purpose, in the same manner, and is also abbreviated to "UT").