仄声

仄聲
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

古时字音分平、上、去、入四声，韵文中称上、去、入三声为「仄声」。

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 声 shēng
  1. sound
  2. voice
  3. tone
  4. noise
  5. reputation
  6. classifier for sounds