An inverted U shape. / An arch-shaped arrangement of trapezoidal stones, designed to redistribute downward force outward. / (architecture) An architectural element having the shape of an arch

To form into an arch shape. / To cover with an arch or arches.

knowing, clever, mischievous / principal; primary

(obsolete) chief

leading, leader

Chief; primary; principal. / First; original. / Highest; most extreme. / (augmentative) Intensely, extremely, or exceptionally.

Curved.

simple past tense and past participle of arch

Abbreviation of archaic. / Abbreviation of architectural.

(uncountable) Abbreviation of archaism. / (uncountable) Abbreviation of archery. / (countable) Abbreviation of archipelago. / (countable) Abbreviation of architect.