Meaning of ARCH in English

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.

—archly adverb

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.