Noun:
1: arch a curved shape in the vertical plane that spans an opening
2: arch a curved bony structure supporting or enclosing organs (especially the inner sides of the feet)
3: arch, archway a passageway under a curved masonry construction; "they built a triumphal arch to memorialize their victory"
4: arch (architecture) a masonry construction (usually curved) for spanning an opening and supporting the weight above it
Verb:
1: arc, arch, curve form an arch or curve; "her back arches"; "her hips curve nicely"
Adjective:
1: patronising, patronizing, arch, superior, condescending (used of behavior or attitude) characteristic of those who treat others with condescension
2: arch, skilled expert in skulduggery; "an arch criminal"