Yes, arch is a Scrabble word!

Verb

1. Form an arch or curve

Adjective

1. (used of behavior or attitude) characteristic of those who treat others with condescension

2. Expert in skulduggery

3. Naughtily or annoyingly playful

Noun

1. A curved shape in the vertical plane that spans an opening

2. A curved bony structure supporting or enclosing organs (especially the inner sides of the feet)

3. A passageway under a curved masonry construction

4. (architecture) a masonry construction (usually curved) for spanning an opening and supporting the weight above it