Capybara \Ca`py*ba"ra\, n. [Sp. capibara, fr. the native name.] (Zo["o]l.) A large South American rodent ({Hydroch[ae]rus capybara}) Living on the margins of lakes and rivers. It is the largest extant rodent, being about three feet long, and half that in height. It somewhat resembles the Guinea pig, to which it is related; -- called also {cabiai} and {water hog}.