Xiàhuá yīn 下滑音 “Downward Slide”

Press a string to the required pitch, pluck the string, the relax the pressure to create a downward slide. May be abbreviated as Xiàhuá 下滑. Ferguson offers the variant Xiàhuá yǐ yīn 下滑倚音 (4) which translates to “Downward Appoggiatura”. It is used for faster rhythms, often as a grace note.

Ferguson also offers Qián huáyīn 前滑音 from Source C but doesn’t offer a description.