神速 (shén sù) literally combines 神 (shén, 'divine' or 'supernatural') and 速 (sù, 'speed' or 'swiftness'), yielding the vivid meaning 'lightning speed' or 'astonishing speed.' It emphasizes extraordinary, almost miraculous rapidity — far beyond ordinary quickness. Unlike neutral terms like 快 (kuài) or 迅速 (xùn sù), 神速 carries a tone of awe or admiration, often implying unexpected or impressive acceleration.

This word is commonly used in descriptive contexts: reporting rapid progress (e.g., recovery, growth, or technological advancement), praising athletic performance, or highlighting sudden developments in news or storytelling. While it can function as a noun ('at lightning speed'), it frequently appears adverbially without 地 (e.g., 发展神速), especially in written Chinese and formal speech. It’s rarely used for everyday minor actions — reserving its impact for truly remarkable velocity or progress.