- A fixed curve traversed by a generatrix in generating a conic section or a cylinder.
- The median line in the trajectory of fire of an artillery piece.
- The first line traced on the ground in laying out a fortification.
- A woman who governs or directs.
- In <em>mathematics</em>, a fixed line, whether straight or not, that is required for the description of a curve or surface.
- In <em>gunnery</em>, the center line in the plane of fire of an embrasure or platform. <em>Tidball.</em> See <internalXref urlencoded="embrasure">embrasure</internalXref>
- A directress.
- A line along which a point in another line moves, or which in any way governs the motion of the point and determines the position of the curve generated by it; the line along which the generatrix moves in generating a surface.
- A straight line so situated with respect to a conic section that the distance of any point of the curve from it has a constant ratio to the distance of the same point from the focus.
- A <xref>female</xref> who <xref>directs</xref>; a <xref>directress</xref>.
- A <xref>line</xref> used to <xref>define</xref> a <xref>curve</xref> or <xref>surface</xref>; especially a line, the <xref>distance</xref> from which a point on a <xref>conic</xref> has a constant <xref>ratio</xref> to that from the <xref>focus</xref>