(idiom) an old warhorse in the stable still aspires to gallop a thousand miles, used to describe an older person who still cherishes great ambitions and spirits, from Cáo Cāo's poem [[步出夏门行|步出夏門行|bu4 chu1 xia4 men2 xing2]]

Literally "an old horse in the stable still dreams of running a thousand miles"; used to describe an older person who still possesses great ambition and energy.