Source : Webster's Revised Unabridged Dictionary (1913)

Sonderclass \Son"der*class`\, n. [G. sonderklasse special
   class.] (Yachting)
   A special class of small yachts developed in Germany under
   the patronage of Emperor William and Prince Henry of Prussia,
   and so called because these yachts do not conform to the
   restrictions for the regular classes established by the rules
   of the International Yacht Racing Union. In yachts of the
   sonderclass, as prescribed for the season of 1911, the
   aggregate of the length on water line, extreme beam, and
   extreme draft must be not more than 32 feet; the weight, not
   less than 4,035 pounds (without crew); the sail area, not
   more than 550 square yards; and the cost of construction (for
   American boats) not more than $2400. The crew must be
   amateurs and citizens of the country in which the yacht was
   built.