肆無忌憚

肆无忌惮
sìwújìdàn
  1. absolutely unrestrained
  2. unbridled
  3. without the slightest scruple

CEDICT

brazen; unbridled; wanton; unscrupulous

Wiktionary

恣意妄為，毫無顧忌。《五代史平話．周史．卷上》：「惟知怨望朝廷，不知己有何功，而敢如此肆無忌憚。」《醒世姻緣傳．第五九回》：「眼中絕不知有公婆，更是肆無忌憚的橫行。」也作「全無忌憚」。

重編國語辭典

形容人恣意妄為，毫無顧忌

維基詞典

Entry Composition

1 肆 sì
  1. four (banker's anti-fraud numeral)
  2. unrestrained
  3. wanton
  4. (literary) shop
2 無忌 wújì
  1. (literary) to lack any scruples
  2. to lack any scruples
3 憚 dàn
  1. dread
  2. fear
  3. dislike

Related entries

囂張 xiāozhāng
  1. rampant
  2. unbridled
  3. arrogant
  4. aggressive
恣意 zìyì
  1. without restraint
  2. unbridled
  3. reckless
恣睢 zìsuī
  1. (literary) reckless
  2. unbridled
  3. self-indulgent
  4. conceited
  5. overly pleased with oneself
恣肆 zìsì
  1. unrestrained
  2. unbridled
  3. free and unrestrained (style)
  4. bold
放肆 fàngsì
  1. wanton
  2. unbridled
  3. presumptuous
  4. impudent
别对我放肆，小姑娘!

Don't get sassy with me young lady!

Source: Tatoeba

大肆 dàsì
  1. wantonly
  2. without restraint (of enemy or malefactor)
  3. unbridled
疏狂 shūkuáng
  1. uninhibited
  2. unrestrained
  3. unbridled