同义词

a. imperceptible

反义词

a.   perceptible

参考例句

1. color is unperceivable to the touch.
颜色是不能被触觉感觉的。
2. an imperceptible drop in temperature; ~an imperceptible nod; color is unperceivable to the touch.
难以觉察的气温下降；轻轻的点头；颜色是不能被触觉感觉的。
3. However, love is unperceivable. You can only know what love is when it's understood and translated.
但是，爱是无法被知晓的，只有当爱被了解和转化的时候，你才会知道什么是爱。

英英解释

adj.
  1. impossible or difficult to perceive by the mind or senses