I. arch 1 /ɑːtʃ $ ɑːrtʃ/ BrE AmE noun [countable]
[ Date: 1200-1300 ; Language: Old French ; Origin: arche , from Latin arcus ; ⇨ ↑ arc ]
1 . a structure with a curved top and straight sides that supports the weight of a bridge or building
2 . a curved structure above a door, window etc
3 . a curved structure of bones in the middle of your foot
4 . something with a curved top and straight sides
II. arch 2 BrE AmE verb [intransitive and transitive]
to form or make something form a curved shape:
Two rows of trees arched over the driveway.
The dog arched its back.
III. arch 3 BrE AmE adjective
[ Date: 1500-1600 ; Origin: arch- in such combinations as arch-rogue and arch-villain ]
amused because you think you understand something better than other people:
‘I think he’s in for a surprise,’ Ian said, in a somewhat arch tone.