You can think of letterbox as a cut for letters: a long, straight-sided opening, or the small box behind it, where something is dropped in and waits to be picked up. Nearly everything the word does seems to grow out of that shape and that job. The slot in a front door and the box in the street are the plain cases. A wide film sitting in a long thin band across a screen borrows the shape. A box hidden on a hill, holding a notebook for the next walker to open, borrows the job.
From the word’s history
The word is transparent: letter + box, a box for letters. The modern uses still show that rectangle and that waiting.
這個字的來歷就寫在字面上：letter（信）加 box（箱子），也就是「裝信的箱子」。今天不管是門上的縫、街上的郵筒，還是螢幕上那條長方形的畫面，都還看得到當初那個形狀。
Wiktionary, "letterbox"
登入就可以看每一支怎麼連回核心畫面。
原始詞典資料7 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。
letterboxnoun
- 1
A box into which mail is put.
- 2
A box into which mail is put.
- A wad of junk mail was pushed through the letterbox in the front door and dropped onto the mat.
- 3
A hidden container that holds a logbook and rubber stamp, found by following clues as a form of recreation.
- 4
hobbieslifestylemountaineeringA rectangular hole or slot.
- His strength was running out fast: one more good letterbox was all that he could conceive himself able to make. He made it, hacking away with slow, painful strokes, his axe-handle slippery with his sweat.
letterboxadj
- 1
broadcastingfilmmediaTransferred to home video formats while preserving the original aspect ratio, having black bars above and below the picture area.
letterboxverb
- 1
broadcastingfilmmediaTo transfer a widescreen motion picture to home video formats while preserving the original aspect ratio, with the placing of black bars above and below the picture area.
- 2
To hunt for letterboxes (containers with logbook and rubber stamp) by following clues.
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。