Rocky is always an adjective, unless you mean the boxer from the movie Rocky Would you like to help me on this issue? 1. I think the rocky should be rock here, am I correct? or No you are not. It should be rocky 2. The noun which is described by rocky is omitted? Not sure I quite get your question, but the noun is outcropping (Strange usage, almost always used as outcrop)

Just to echo what Ka-How said, I don't think I've ever seen "rocky" used as a noun (unless you're using it as someone's name); so it's definitely used as an adjective here. The word it's describing is "outcropping," which means the part of a rock that is protruding out of the earth. "Rocky outcrop" is a phrase that's often used.

As far as I know, rocky is always used as an adjective. The only exception I know of is the protagonist Rocky Balbao from the Rocky film series. The noun is "outcropping", which is apparently "rocky", and yes the adjective "rocky" does relate to rocks. Perhaps the author used rocky to describe that the outcropping is dangerous because of the rock formation and therefore one should not go down there to retrieve the boot? I'm not entirely sure. Merriam describes the word "outcrop" as: 1 : a coming out of bedrock or of an unconsolidated deposit to the surface of the ground 2 : the part of a rock formation that appears at the surface of the ground

In all honesty, I don't have the terminological knowledge to answer this; however, what I do know is that Oxford dictionary recognises both "outcropping (n)" and "outcrop (n/v)". Wikidiff states this: "As nouns the difference between outcrop and outcropping is that outcrop is a piece of land that stands out (usually into water) from the land surrounding while outcropping is an outcrop. As a verb outcrop is (geology|of a stratum) to come out to the surface of the ground." In short, I believe it would be best to ask an expert with experience to explain the differences (or ask the author). I'm sorry I couldn't give you a clear answer on this.