The term 'rainbow-shaped' can be described by the 5-letter word 'ARCED'. An arc is a curved line that forms a part of the circumference of a circle, or any shape approximating a curve. Therefore, when something is said to be 'ARCED', it means that it has a curved shape, like a rainbow. A rainbow is an optical phenomenon that appears in the sky as a multicolored arc of light, usually seen after a rainstorm. The colors of a rainbow are typically red, orange, yellow, green, blue, indigo, and violet.