When a geometry is described by a set of axioms, the notion of a line is usually left undefined (a so-called primitive object). The properties of lines are then determined by the axioms which refer to them.
Definition of mull 1: friable forest humus that forms a layer of mixed organic matter and mineral soil and merges gradually into the mineral soil beneath 2: a finely powdered solid especially in a suspension
lull. 1. to put to sleep or rest by soothing means: to lull a child to sleep with singing. 2. to soothe or quiet. 3. to give or lead to feel a false sense of safety. 4. to quiet down; let up; subside: furious activity that finally lulled.