老当益壮 lǎodāngyìzhuàng

(1) [hale and hearty in old age; be old but vigorous]∶主要指老年人继续保持旺盛的斗志

丈夫为志,穷当益坚,老当益壮。——《后汉书·马援传》

(2) [florid old; be old in age but buoyant in spirit; there's many a good tune played on an old fiddle]∶年纪虽老,仍健康和充满活力

老当益壮,不甘落后