一落千丈

1. • lit. to drop a thousand zhang in one fall (idiom)
2. • fig. (of business, popularity etc) to suffer a sudden, devastating decline
3. • to take a dive

Character by character

• 一(yī)one
• 落(luò)fall or drop
• 千(qiān)thousand
• 丈(zhàng)measure of length, ten Chinese feet