इह in this world, गच्छन्ति are passing, अहोरात्राणि days and nights, ग्रीष्मे in summer, अंशवः rays of the sun, जलमिव like the water, सर्वेषाम् all, प्राणिनाम् living things', आयूंषि life span, आशु are quickly, क्षपयन्ति are decaying.

The passing days and nights quickly decrease the life span of all living beings in this world, like sunrays drying up the water in summer.