From Longman Dictionary of Contemporary Englishldoce_008_aarcharch1 /ɑːtʃ $ ɑːrtʃ/ ●●○ noun [countable] 1 
AAa structure with a curved top and straight sides that supports the weight of a bridge or building2 AAa curved structure above a door, window etc3 HBHa curved structure of bones in the middle of your foot4 CFsomething with a curved top and straight sides
AAa structure with a curved top and straight sides that supports the weight of a bridge or building2 AAa curved structure above a door, window etc3 HBHa curved structure of bones in the middle of your foot4 CFsomething with a curved top and straight sidesExamples from the Corpus
arch• It also has a horseshoe arch entrance to the sanctuary, but its decoration is poorer than that at S. Juan.• Sculptures of angels dance among the soaring arches that form the ceiling of the mission.• More thick dry stone arches connect the two ruins and lead the eye into a singular landscape.• Graffiti covered the arch at the base of Fifth Avenue.• Repeat for the other side of the arch.• The arch is a beacon for folks heading West.• It was built as a triumphal arch for King Matthias in 1614.archarch2 verb [intransitive, transitive] BENDto form or make something form a curved shape Two rows of trees arched over the driveway. The dog arched its back.→ See Verb tableExamples from the Corpus
arch• The bar extends along the left wall with a stuffed marlin arched above it that I suspect was never really alive.• Thick white branches arch as far out as the tree is tall, sometimes at seemingly impossible angles.• The dog arched its back and showed its teeth.• Rachel daintily arched one eyebrow as if I had mentioned inviting her servants to some feast or revelry.• The private swans arch out their feathers and preen and nourish themselves.• They arch out to a five-foot width, then narrow quickly toward the bow and stern.• Strings of spittle hanging from pointed teeth to lower lip reflected moonshine as the cadaverous head arched skywards.archarch3 adjective FUNNYamused 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 adverbExamples from the Corpus
arch• His soulless eyes are narrowed and sullen, and his arch goatee recalls an amoral Transylvanian count.• He was right, in the arch sense that he meant it, as a means of chiding overanxious environmentalists.• an arch tonearch-arch- /ɑːtʃ, ɑːk $ ɑːrtʃ, ɑːrk/ prefix XXbelonging to the highest class or rank an archbishop (=an important bishop) our archenemy (=our worst enemy) the company’s arch-rivals (=main competitors)Examples from the Corpus
arch-• the company's archrivalsOrigin arch- Old French Latin arch-, archi-, from Greek, from archein “to begin, rule” arch1 (1200-1300) Old French arche, from Latin arcus; → ARC arch3 (1500-1600) arch- in such combinations as arch-rogue and arch-villain 