'Springing line of an arch' definitions:

Definition of 'Springing line of an arch'

From: GCIDE

Springing \Spring"ing\, n.
1. The act or process of one who, or that which, springs. [1913 Webster]
2. Growth; increase; also, that which springs up; a shoot; a plant. [1913 Webster]
Thou blessest the springing thereof. --Ps. lxv. 10. [1913 Webster]
Springing line of an arch (Arch.), the horizontal line drawn through the junction of the vertical face of the impost with the curve of the intrados; -- called also spring of an arch. [1913 Webster]