In the study of languages, a literal translation of a foreign language text. Really useful ponies have the original text on one page and the translation on the facing page. So called because they "carry" students, saving them the pedestrian labour of translating on their own.
The Loeb Classical Library produces a superb set of ponies of Latin and Greek texts, with green covers for the Greek and red for the Latin. Richmond Lattimore's translations of the Iliad and Odessey are also useful, since the line numbers and content correspond to the original Greek.
Note that most lecturers own copies of the ponies for their courses, and are quick to recognise (and penalise) the translated text. However, ponies have their place: they are extremely useful for finding a specific section of the original text. They can also help beginners get the sense of a passage before doing a proper translation.