Precipitous (adjective)

1. Steep, almost vertical.
2. Performed or done suddenly and without careful consideration.
3. Characterized by a steep incline or descent.

Origin:

The word precipitous comes from the latin word praecipitare, meaning "to throw headlong" and it has been in use since the 16th century.

Examples:

1. The mountain had a precipitous drop.
2. He took a precipitous decision.
3. The road was steep and precipitous.
4. The stock market had a precipitous fall.
5. The company's precipitous decline surprised everyone.