cliff, bluff, precipice
崕 centers on a steep, vertical rock face: a cliff, bluff, or precipice.
崕 combines 山 (mountain) with 厓, which likely contributes both sound and the idea of a steep edge or cliff. The exact historical development of 厓 is uncertain.
The left side is a mountain 山, and the right side 厓 looks like a steep drop-off. Picture a mountain with a sheer cliff face.
For ガイ, imagine a guy standing at the edge of a cliff: guy -> ガイ, and he's looking down the precipice.