This is the 11115th most frequent Russian word.
горной
"Горной" means "mountain" or "mountainous" in English, related to mountains.
Here, the word "горной" describes the adjective "mountain" in the instrumental case, modifying "тропе" (trail)
Я люблю гулять на горной тропе.
I enjoy walking on the mountain trail.
In this case, "горной" is the adjective "mountain" in the genitive case, modifying "реки" (river)
В горах я почувствовал свежесть горной реки.
In the mountains, I felt the freshness of the mountain river.
Here, "горной" is modifying the name "Лукой" and indicates a thematic or locational characteristic linked to "mountain".