steep slope; sudden drop; precipitous incline
Describes a road, path, or terrain that drops or rises sharply. Often used literally, but can appear in figurative contexts for a sudden decline.
There's a steep slope ahead, so please dismount and walk your bicycle.
There were many steep slopes on the mountain trail.
Phrase composed of 急 (きゅう, 'steep, sudden') + な (attributive form of auxiliary) + 坂 (さか, 'slope'). A straightforward descriptive compound.