Waters that rush in a vast, headlong flood; a road precipitous, narrow, and strait.

Torrent against footpath — the two halves of the line set the whole scene: something enormous moving fast, and something very narrow to cross it on.

Solemn as a bolt of white silk flung across the Yangtze; yet like a fire-pit floating up to the world above.

疋練, pǐ liàn, is a bolt of undyed white silk, the standard image for a pale ribbon of water or road seen from above. 長江 is the Chángjiāng, the Yangtze. 似 is sì. The bridge looks like a length of silk thrown across the largest river in China — and also like a fire-pit floating up from below.

A shadow-vapor presses upon one, cold piercing to the bone; a reeking wind assails the nose, its stench boring to the heart.

腥風 is a wind carrying the smell of blood or raw fish. 鑽 is zuān, to bore through.

Waves overturning, billows rolling — for those who come and go there is no boat to ferry them across;

並沒 is "there is none whatever"; 沒 is méi. No ferry — which is precisely the terror of the place. The bridge is the only way, and look at it.

Bare of foot and wild of hair, all who come and go are sin-working ghosts.

作業鬼 are ghosts who made karma, meaning bad karma: the ones who piled up deeds they now have to pay for. 盡 is jìn.

The bridge is several lǐ long, only three zhā across, a hundred chǐ high, and a full thousand-fold deep.

The measurements are the horror. Several lǐ long, a hundred chǐ high, a thousandfold deep — and three 㪥 wide. That character is rare enough that its reading, zhā, and its value as a measure are both uncertain; other editions of the novel carry a different unit in the slot. Whatever it is, it is small, and that is the whole point of the line. 長 is cháng; 尺 is chǐ, a Chinese foot; 里 is lǐ. 重 here is chóng, a layer or fold.

Above, no handrail or balustrade; below, fiends that snatch at men.

搶人, qiǎng rén, is to snatch at people. No handrail above; below, things waiting for anyone who slips.

Cangues and manacles wound about their bodies, they are driven onto the perilous road of the Nai.

枷杻, jiā chǒu, are the cangue and the handcuffs — the cangue being the heavy wooden collar locked round a prisoner's neck in Chinese justice, worn in public as both restraint and humiliation. The damned are driven onto the bridge in full judicial hardware.

Behold, at the bridge's edge, the spirit-generals, how fierce and truculent; within the river, the sinful souls, how truly wretched.

神將, shén jiàng, are spirit-generals. 甚 is shèn, "how very." 孽魂 are souls weighed down with sin.

On the forking branches of the trees hang robes of silk in green and red, yellow and purple;

枒杈, yā chā, is a forked branch. The bright silks hanging in the trees were stripped from the dead — a detail that turns the riverbank into something between a gallows and a laundry line.

before the sheer cliff-face crouch the lewd and railing shrews who cursed their husbands' parents.

壁斗崖 is a sheer drop of a cliff, with 斗 as dǒu, "steep." And then the poem gets oddly specific: 毀罵公婆, women who abused their husbands' parents. Of all the sins available, this is the one singled out by name at the Nai — a reminder of whose morality is doing the sentencing.

Copper serpents and iron dogs are left to fight over their flesh; forever fallen into the Nai, they have no way out.

銅蛇鐵狗, copper snakes and iron dogs, are the standing beasts of Chinese hell imagery. 永墮 is "fallen for ever." The rhapsody signs off on damnation without parole.