high, steep, lofty, towering
嶸 centers on extreme verticality: a mountain that is high, steep, lofty, or towering. All given meanings describe a dramatic, imposing upward rise.
嶸 combines 山 (mountain) with 榮, which likely contributes the sound and reinforces the idea of flourishing or towering height. The exact historical development of the right component is uncertain.
The left side is a mountain 山, and the right side 榮 looks like a tall, ornate structure with a roof and trees. Picture a mountain so high it seems to support a towering, flourishing palace.
For コウ, imagine a towering mountain so high it scrapes the sky, and a climber shouts 'Go!' (コウ) as they begin the steep ascent.