Rankine (or degrees Rankine) is a scale of temperature derived from an imperial unit and is denoted by the symbol °R.
Rankine is defined as a vector or shift from the Farenheit scale. Like the Kelvin (but 11 years later in 1859), it was also developed by a physicist from Glasgow University - namely William John Macquorn Rankine and was proposed to be used in engineering systems where heat computations are done in degrees Farenheit rather than Celsius.
Zero on both the Kelvin and Rankine scales is absolute zero (infinite cold - or the absolute absence of any thermal energy whatsoever).
The boiling point of water is 671.64102 °R. The freezing point of water is 491.67 °R.