is a depression
A meatus is an opening; therefor, it's a depression, not a projection.
projection
projection
projection
projection
....opening?
A fissure is an opening or crack in the Earth's crust, typically where tectonic plates meet. It is not a projection or depression, but rather a narrow, long fracture in the ground.
Ramus.
The plural of meatus is meatuses or meatus - both forms are accepted.
"A crest is a projection or ridge, especially of bone; cresta"source: chacha.com
projection. The bumps of bone around your knees and elbows are almost all called condyles.
A meatus is a tubular opening or passage in the body.