The Collaborative International Dictionary of English v.0.48:

Celsius \Cel"si*us\, n.
   The Celsius thermometer or scale, so called from Anders
   Celsius, a Swedish astronomer, who invented it. It is the
   same as the centigrade thermometer or scale.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Celsius
    n 1: Swedish astronomer who devised the centigrade thermometer
         (1701-1744) [syn: Celsius, Anders Celsius]