The Collaborative International Dictionary of English v.0.48:
Leading \Lead"ing\, a.
Guiding; directing; controlling; foremost; as, a leading
motive; a leading man; a leading example. -- Lead"ing*ly,
Leading case (Law), a reported decision which has come to
be regarded as settling the law of the question involved.
Leading motive [a translation of G. leitmotif] (Mus.), a
guiding theme; in the musical drama of Wagner, a marked
melodic phrase or short passage which always accompanies
the reappearance of a certain person, situation, abstract
idea, or allusion in the course of the play; a sort of
musical label. Also called leitmotif or leitmotiv.
Leading note (Mus.), the seventh note or tone in the
ascending major scale; the sensible note.
Leading question, a question so framed as to guide the
person questioned in making his reply.
Leading strings, strings by which children are supported
when beginning to walk.
To be in leading strings, to be in a state of infancy or
dependence, or under the guidance of others.
Leading wheel, a wheel situated before the driving wheels
of a locomotive engine.