1. 不能下定义的：indefensibly 不能防御地 | indefinable 不能下定义的 | indefinably 不能下定义地
2. 难下定义的：indecomposable 不可分解的 | indefinable 难下定义的 | indefinite form 不定形式
3. 不能下定义的; 不确定的 (形)：indefensible 不能防卫的, 无辩护余地的 (形) | indefinable 不能下定义的; 不确定的 (形) | indefinite article 不定冠词
4. 不可名状的：obtainable 可得到的 | indefinable 不可名状的 | abominable 可恶的
1. 难以确切表达的;难以确定的;模糊不清的
An indefinable quality or feeling cannot easily be described.
e.g. There was something indefinable in her eyes...
她的眼神里有种难以确定的东西。
e.g. His head felt lighter in some indefinable way.
他的头不知为何有点晕眩。
1. On the other hand, they have an indefinable mistrust of foreign capital and labor.
2. He has the same devilish charisma, aura of mystery and indefinable magnetism that make women swoon and men envious.
adj
1. not capable of being precisely or readily described
not easily put into words
e.g. an indefinable feeling of terror
an abstract concept that seems indefinable
Synonym: undefinable
2. defying expression or description
e.g. indefinable yearnings
indescribable beauty
ineffable ecstasy
inexpressible anguish
unspeakable happiness
unutterable contempt
a thing of untellable splendor
Synonym: indescribable ineffable unspeakable untellable unutterable