形容詞 indistinguishable:

1. exactly alike; incapable of being perceived as different
   同義詞：identical
2. not capable of being distinguished or differentiated
   同義詞：undistinguishable

1. Its colour makes the moth indistinguishable from the branch it rests on.
   這蛾子停在樹枝上，其顏色和樹枝幾不可辨。

in.dis.tin.guish.a.ble

adj.（形容詞）
Not distinguishable, especially:
無差別的：尤指難以區(qū)分的
Impossible to differentiate or tell apart:
難分辨的：不可能去區(qū)分或識別：
例句：
indistinguishable twins; a moth with markings that make it indistinguishable from its background.
難以分辨的雙胞胎；蛾翅膀上的斑紋使得它與背景無法分辨

Impossible to discern; imperceptible:
不易察覺的：不可能識別的；難以覺察的：
例句：
a sound that was indistinguishable to the human ear.
一種為人耳不易察覺的聲音

Difficult to understand or make out; vague:
難以理解或辨別的；模糊的：
例句：
indistinguishable speech.
難以理解的談話

【引伸】
in.distin.guishableness 或
in.distin.guishabil.ity
n.（名詞）
in.distin.guishably
adv.（副詞）