One way to picture it: you are on a slope and the ground ahead falls away — from here on, gravity is doing the moving for you, whether that is a relief or a slide you cannot stop.
From the word’s history
Simply down + hill — the meaning is transparent and the metaphors grow straight out of the physical picture.
這個字就是 down（往下）加 hill（山坡）拼起來的，沒有藏著什麼外來字根。正因為它字面透明，後面幾個比喻用法都是直接從「往下坡」這個看得見的畫面延伸出去的，不需要繞路理解。
Wiktionary: downhill (from down- + hill)
登入就可以看每一支怎麼連回核心畫面。
原始詞典資料11 筆記錄
以下是外部詞典記錄的用法，摘錄並精簡格式，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
Downhillname
- 1
A coastal village and beach (Downhill Strand) in County Londonderry, Northern Ireland.
- 2
A hamlet in St Eval parish, Cornwall, England (OS grid ref SW8669).
- 3
A northern suburb of Sunderland, Tyne and Wear, England (OS grid ref NZ3559).
downhilladv/ˌdaʊnˈhɪl/
- 1
Down a slope.
- Because we got to the summit of the mountain, we could only go downhill from there.
- I worked my way downhill, slip sliding in the mud along a steep embankment that followed a stream until it emptied into a creek.
- 2
So as to deteriorate or get worse.
- After Don made those tasteless remarks, our relationship with him went downhill.
downhilladj/ˈdaʊnˌhɪl/
- 1
Located towards or at the bottom of a slope or hill.
- Moraines are found at the downhill end of a glacier.
- 2
Going down a slope or a hill.
- This year's race is on a downhill course.
- It was nearly all downhill into Shrewsbury, with two intermediate stops, and a grand sequence of long curves around which Soult nuzzled her way with a quick side-to-side action.
- 3
Easy.
- That's the hard part of the job done. From now on it's downhill all the way.
downhillnoun/ˈdaʊnˌhɪl/
- 1
The fastest of the disciplines of alpine skiing.
- 2
A rapid descent of a hill in related sports, especially in alpine skiing.
downhillverb
- 1
To take part in downhill skiing.
摘錄自 英文維基詞典 English Wiktionary，已精簡格式；依 CC BY-SA 4.0 授權使用，改動後的內容同樣以此授權提供。