仄聲

仄声
zèshēng
  1. oblique tone
  2. nonlevel tone
  3. uneven tone (the third tone of Classical Chinese)

CEDICT

oblique tone (a category of tones in classical Chinese, consisting of the rising tone (上聲／上声 (shǎngshēng)), the departing tone (去聲／去声 (qùshēng)), and the entering tone (入聲／入声 (rùshēng)).)

Wiktionary

古時字音分平、上、去、入四聲，韻文中稱上、去、入三聲為「仄聲」。

重編國語辭典

Entry Composition

1 仄 zè
  1. to tilt
  2. narrow
  3. uneasy
  4. oblique tones (in Chinese poetry)
2 聲 shēng
  1. sound
  2. voice
  3. tone
  4. noise
  5. reputation
  6. classifier for sounds