From Wiktionary, the free dictionary
Literally, “in the scare”.
no susto
- Used other than figuratively or idiomatically: see no, susto.
- as an involuntary response to a sudden scare; with a startle
Caí no susto.- I fell down with a startle.
- as a response to an urgent need
Ela teve que aprender alemão no susto.- She had to learn German quickly.