眼睛看得到的邊界不清楚
這一族就是畫面本身：實際存在、但邊緣淡掉或從來沒標死的東西。
adjective · B2
Not clearly marked, or without a clear edge or shape, so you cannot see exactly where the thing begins and ends.
輪廓模糊
核心畫面
Picture something whose edge you cannot find. The thing is there — a path, a patch of fog, a job, a rule — but when you look for the line that says here it stops, there is no line, only a fade. Ill-defined can be thought of as that missing edge. Sometimes the edge is a real one you would see with your eyes, and sometimes it is made of words.
可以想成一個東西，你找不到它的邊。東西是在那裡——一條山徑、一片霧、一份工作、一條規則——可是當你去找「到這裡為止」…更多收起
可以想成一個東西，你找不到它的邊。東西是在那裡——一條山徑、一片霧、一份工作、一條規則——可是當你去找「到這裡為止」的那條線時，線並不存在，只有慢慢淡掉。ill-defined 可以想成就是那條不見了的邊。有時候那條邊是眼睛看得到的，有時候那條邊是用文字畫出來的。From the word’s history
Wiktionary records the word as ill + defined. Here ill is the older adverb meaning badly, the same ill as in ill-prepared and ill-timed, and define carries the idea of setting a boundary — so the compound says the boundary was set badly.
來源資料記錄這個字是 ill 加上 defined。這裡的 ill 是舊的副詞用法「不好地」，跟 ill-prepared、ill-timed 是同一個 ill；define 本身帶有「畫出界線」的意思。所以整個字字面上就是「界線畫得不好」，跟上面那個「找不到邊」的畫面剛好對得上。
Evidence packet, Wiktionary entry for ill-defined (source_ref kaikki:3f6f69a190036ae4:1671735184:2507), etymology_text: 'From ill + defined.'
Two branches
用文字畫出來的界線不清楚
同樣是找不到邊，只是這條邊不是用眼睛看的，而是用定義、規則、說明寫出來的。
adjective · B2
Not described or explained clearly enough, so nobody can tell exactly what is included, what is meant, or what is expected.
界定不清