Now that dragon, having eaten Sanzang's white horse, lay low in the middle of the gorge-bed, nursing its spirit and biding quietly — when it heard someone hurling abuse and demanding a horse.

潛靈養性, "to sink the spirit and nourish one's nature," is Daoist self-cultivation vocabulary, applied here with a touch of irony to a dragon digesting a stolen horse. 索馬, "to demand the horse." The two 那 are demonstrative (nà); 聽得 takes resultative 得 (de).

Unable to hold down the fire rising in its heart, it flung itself up in a rush, leaping through the waves and churning the billows, and sprang to the surface crying: "Who is it that dares run his mouth and insult me here?"

按不住, "unable to press down"; 跳將上來, "to leap up," 將 the directional particle (jiāng). 海口, literally "a sea-sized mouth," means loud, boastful abuse; 那個 is interrogative — "who" — hence nǎ.

The Pilgrim, seeing it, gave a great roar: "Stay where you are! Give me back my horse!"

大咤一聲, "to give a great shout" (咤, zhà). 休走, "don't flee, stay"; 還我馬來, 還 read huán. The taunt has done its work: dragon and monkey stand face to face.

Swinging his cudgel, he struck straight at its head.

掄 (lūn) is to brandish or swing, the durative 著 read zhe; 劈頭, right at the head, full in the face.

The dragon bared its fangs and flailed its claws and came clawing at him.

張牙舞爪 (zhāng yá wǔ zhǎo), "to bare fangs and brandish claws," is the set phrase for a beast in ferocious attack. 那條 is demonstrative (nà).

The bout the two of them fought there at the edge of the gorge was fierce indeed. And this was the sight of it:

賭鬥, "to fight it out, a contest"; 驍雄 (xiāoxióng), "valiant, fierce." 但見那 is the lead-in ushering in the descriptive verse that follows.

The dragon unfurled its keen claws; the monkey raised his golden hoop.

A tight four-plus-four opening. 舒 is to stretch out, unfurl; 金箍, the gold-hooped staff. The rhapsody (賦) sets the two combatants in strict parallel, blow answering blow.

That one — its whiskers hung down like threads of white jade; this one — his eyes flashed like lamps of ruddy gold.

那個…這個 ("that one… this one") are the balanced demonstratives (nà… zhè) that structure the whole set-piece, dragon set against monkey. 鬚垂白玉線 and 眼幌赤金燈 match feature to feature — the dragon's jade-thread whiskers, Wukong's lamp-bright eyes.

That one — the bright pearl beneath its whiskers spat out a coloured mist; this one — the iron staff in his hand whirled up a wild wind.

The parallel deepens: the dragon's 明珠 (its treasured pearl) against Wukong's 鐵棒 (the iron staff), mist against wind. 手中 is zhōng; 那個 demonstrative nà.

That one is a wretch of a son who wronged his own parents; this one is a sprite who once bullied the generals of Heaven.

The couplet names each combatant's history. 迷爺娘的業子: 業子 ("a karma-child, a wayward son," 子 read zǐ) glances at the dragon's offence against its parents, for which it was condemned to the gorge. 欺天將: 天將 is "the generals of Heaven" (將 read jiàng), whom Wukong routed in his revolt; 妖精, a sprite or monster.

The two of them, each for the tribulations laid upon him, had suffered grinding hardship; now, to win through, each put forth all his power.

都 ("both," dōu) binds the pair: dragon and monkey alike are bound to the pilgrimage by karmic 難 (nàn) — "tribulation, ordeal," the calamitous sense, not that of mere difficulty. 磨折, "torment, grinding hardship"; 各顯能, "each displaying his prowess." The rhapsody frames the duel, aptly, as two sufferers of destiny contending.