In architecture, a molding whose profile is a semicircle. It may be either a bead or a torus.(noun)
Semicircular or semicylindrical: as, a half-round file, etc.
The Century Dictionary (Public Domain)
Use "half-round" in a sentence
"I was unable to get additional information on it, but it is chambered in. 30-'06 with a half-round, half-octagon barrel, and topped (of course) with a Leupold variable."
"She was slicing them into these half-round rainbows."
"Congenital tracheal stenosis (narrowing due to a birth defect) is a rare condition in which the cartilage "rings" in the trachea, normally two half-round pieces of cartilage facing one another, fuse together into solid rings during fetal development."