拿來出恭 Only Good For A Chamber Pot
那行者將身一抖，收了剝去的衣服，現本相，跳出洞外，回頭罵道：「妖精不要無禮。瓶子鑽破，裝不得人了，只好拿來出恭。」喜喜歡歡，嚷嚷鬧鬧，踏著雲頭，徑轉唐僧處。那行者将身一抖，收了剥去的衣服，现本相，跳出洞外，回头骂道：「妖精不要无礼。瓶子钻破，装不得人了，只好拿来出恭。」喜喜欢欢，嚷嚷闹闹，踏着云头，径转唐僧处。
逐句解 Line by line
Wukong gave himself a shake, gathered up the clothes they had stripped off him, showed his true form, sprang out of the cave and turned back to curse them: "Demons — none of your insolence!
現本相 takes 相 at xiàng, appearance. And note the theft: he stops on the way out to collect the clothes they took off him before the bottling. The undressing that made the trap work is now an insult he can carry away.
"Your bottle is bored through. It won't hold a man any more. It's only good to squat over."
裝不得人 puts 得 in the light de, the cannot-manage-to grammar. 出恭 is a wonderfully prim euphemism for relieving oneself — it comes from the wooden tablet marked gōng that examination candidates had to carry when they left the hall for the latrine, and it became the polite word for the errand itself. He is calling the cosmos-in-a-jar a commode, in the language of the civil service examinations.
Delighted with himself, whooping and racketing, he trod the cloud-tops and went straight back to where the Tang monk was.
嚷 is rǎng, to shout — and the doubled form is a small trap, because an unguarded reading gives two different wrong tones to the two halves of the same word. 踏著雲頭 takes the light zhe.
The insult is precisely aimed. Two passages of cosmology went into that bottle — the trigrams, the solar terms, the Northern Dipper — and Wukong's review is that it now has a hole in the bottom and would do for a chamber pot. The novel spends its metaphysics and then lets the monkey price it.
出恭 is worth the note it gets. A word invented by examination bureaucracy for the most basic bodily need is the perfect register for this chapter, which has been running a demon cave as a government office since the third gate. He is not being crude. He is being crude in officialese.