深不可测

深不可測
shēnbùkěcè
  1. deep and unmeasurable (idiom); unfathomable depths
  2. incomprehensible
  3. enigmatic and impossible to predict

CEDICT

unfathomable; impossible to understand

Wiktionary

深得无法测量出来。形容非常深远，难以测知。

重編國語辭典

Entry Composition

=1 深 shēn old variant of 深 shēn
=1 深 shēn deep (lit. and fig.)
2 不可 bùkě cannot; should not; must not
3 测 cè
  1. to survey
  2. to measure
  3. to conjecture

Related entries

难以理解 nányǐlǐjiě
  1. hard to understand
  2. incomprehensible
你难以理解女人和小孩子对你说的话吗？

Do you have difficulty understanding what women or small children say to you?

Source: Tatoeba

不知所谓 bùzhīsuǒwèi
  1. nonsense
  2. nonsensical
  3. incomprehensible
  4. to make no sense
费解 fèijiě
  1. to be puzzled
  2. hard to understand
  3. unintelligible
  4. incomprehensible
這事費解得很。

This is extremely confusing.

Source: Tatoeba