The phrase "in the form of an arch" can be described with various synonyms to provide different shades of meaning. Some possible words are arched, rounded, curved, bent, bowed, vaulted, concave, and lobed. Each word has its own nuance and can be used to evoke a certain feeling or imagery. For example, arched emphasizes the graceful and elegant sweep of the curve, while vaulted suggests a grandeur and solidity. Regardless of which synonym is chosen, they all convey a sense of fluidity, movement, and organic shape, adding visual interest and drama to any architectural or design element.