非同小可

fēitóngxiǎokě
  1. extremely important
  2. no small matter

CEDICT

no small (or trivial) matter

Wiktionary

  1. 形容事情的重要或情況嚴重。
  2. 形容人的學問或本領不同尋常。《儒林外史．第四七回》：「話說虞華軒也是一個非同小可之人。」《文明小史．第二九回》：「這位大紳鄉非同小可，乃曾做過出使英國欽差大臣。」也作「非通小可」。

重編國語辭典

Entry Composition

1 非 fēi
  1. to not be; not
  2. wrong; incorrect
  3. non-; un-; in-; de-
  4. to reproach; to blame
  5. (coll.) to insist on; simply must
2 同 tóng
  1. like
  2. same
  3. similar
  4. together
  5. alike
  6. with
3 小可 xiǎokě
  1. small
  2. unimportant
  3. (polite) my humble person

Related entries

至關重要 zhìguānzhòngyào
  1. extremely important
  2. vital
  3. crucial
  4. essential
摩天大厦里的电梯是至关重要的。

The elevators in a skyscraper are vital systems.

Source: Tatoeba

切要 qièyào
  1. essential
  2. extremely important