Semicircular means shaped like half of a circle. If you cut a perfectly round pizza straight down the middle, each piece would have a semicircular edge. Anything semicircular curves in a smooth arc like half a circle.

You'll see semicircular shapes all around you. Many windows above doors are semicircular, called fanlight windows. Ancient Roman architects loved building semicircular arches for doorways and bridges because this shape distributes weight efficiently. Some amphitheaters have semicircular rows of seats that curve around the stage. Even the path you walk when circling halfway around a fountain is semicircular.

In your ear, tiny semicircular canals filled with fluid help you keep your balance. When you spin around and feel dizzy, that's the fluid in your semicircular canals still sloshing around after you've stopped.

The word describes anything with that distinctive half-circle curve: a semicircular driveway that loops in front of a building, a semicircular table pushed against a wall, or the semicircular motion of a clock's minute hand traveling from twelve to six o'clock.