leading (n.1)

"lead work; lead covering or frame of lead," mid-15c., verbal noun from lead (n.1). Printing sense is from 1855.

leading (n.2)

mid-13c., "a bringing by force," verbal noun from lead (v.1). Meaning "direction, guidance" is from late 14c.

leading (adj.)

1590s, "that goes first," present-participle adjective from lead (v.1). Meaning "directing, guiding" is from 1620s. Of persons, "having first or most prominent place," 1670s. In reference to theatrical companies, leading lady is from 1846; leading man from 1847.

Definitions of leading
leading (adj.)
having the leading position or higher score in a contest;
the leading team in the pennant race
Synonyms: ahead / in the lead
leading (adj.)
greatest in importance or degree or significance or achievement;
the country's leading poet
Synonyms: preeminent
leading (adj.)
indicating the most important performer or role;
the leading man
Synonyms: prima / star / starring / stellar
leading (adj.)
going or proceeding or going in advance; showing the way;
we rode in the leading car
the leading edge of technology
leading (n.)
the activity of leading;
Synonyms: leadership
leading (n.)
thin strip of metal used to separate lines of type in printing;
Synonyms: lead