And by the definition of one of the two major Taiwanese political parties as well. From Wikipedia:

"The Kuomintang holds the "One China Principle" and maintains its claim that under the ROC Constitution (passed by the Kuomintang government in 1947 in Nanjing) the ROC has sovereignty over most of China (including by their interpretation both mainland China and Taiwan)...Former ROC President Ma Ying-jeou had re-asserted claims on mainland China as late as October 8, 2008."