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
mullein. n. 1. (Plants) any of various European herbaceous plants of the scrophulariaceous genus Verbascum, such as V. thapsus (common mullein or Aaron's rod), typically having tall spikes of yellow flowers and broad hairy leaves.See also Aaron's rod.oun. 1. mullein-any of various plants of the genus Verbascum having large usually woolly leaves and terminal spikes of yellow or white or purplish flowers.