一驚一乍

frightened / flustered

one / single / a (article) / as soon as / entire; whole; all; throughout / "one" radical in Chinese characters (Kangxi radical 1) / also pr. [yao1] for greater clarity when spelling out numbers digit by digit

to startle / to be frightened / to be scared / alarm

at first / suddenly / abruptly / to spread / (of hair) to stand on end / bristling