edge, brink, rim (outer part of something) / ledge, margin / skin (layer of solid matter that forms on top of a liquid in a vessel)

(idiomatic) to go wild

random (selected for no particular reason) / random (apropos of nothing, lacking context) / random (often saying random things)

(colloquial, youth language) A rando, a random. (An arbitrary person with whom one has no shared social connection.)