Definitions of arch:

noun: (architecture) a masonry construction (usually curved) for spanning an opening and supporting the weight above it
noun: a passageway under an arch
noun: a curved bony structure supporting or enclosing organs (especially arches of the feet)
noun: a curved shape in the vertical plane that spans an opening
verb: form an arch or curve
Example: "Her back arches"
adjective: (used of behavior or attitude) characteristic of those who treat others with condescension
name: A surname (very rare: popularity rank in the U.S.: #20407)