To cover with a vault, or span with an arch.
                  
                
                  
                    
                    To throw into the shape of an arch or vault; curve: as, the horse arches his neck.
                  
                
                  
                    
                    To form an arch or arches: as, the sky arches overhead.
                  
                
                  
                    noun. 
                    Chief; principal: a prefix much used in composition with words both of native and of foreign origin. See arch.
                  
                
                  
                    
                    Chief; principal; preëminent. See arch-.
                  
                
                  
                    
                    Cunning; sly; shrewd; waggish; mischievous for sport; roguish: now commonly used of facial expression: as, “so arch a leer,”
                  
                
                  
                    noun. 
                    A chief; a leader.
                  
                
                  
                    noun. 
                    A box or chest; in plural, archives.
                  
                
                  
                    noun. 
                    The ark of Noah.
                  
                
                  
                    noun. 
                    The ark of the covenant.
                  
                
                  
                    noun. 
                    1. In geometry, any part of the circumference of a circle or other curve; an arc. See arc
                  
                
                  
                    noun. 
                    In architecture, a structure built of separate and inelastic blocks, assembled on a curved line in such a way as to retain their position when the structure is supported extraneously only at its two extremities.
                  
                
                  
                    noun. 
                    Any place covered with an arch or a vault like an arch: as, to pass through the arch of a bridge.
                  
                
                  
                    noun. 
                    Any curvature in the form of an arch: as, the arch of the aorta; the arch of an eyebrow, of the foot, of the heavens, etc.
                  
                
                  
                    noun. 
                    In mining, a portion of a lode left standing, either as being too poor for profitable working or because it is needed to support the adjacent rock.
                  
                
                  
                    noun. 
                    The roofing of the fire-chamber of a furnace, as a reverberatory or a glass-furnace; hence, sometimes, the fire-chamber itself.