Webster's Revised Unabridged Dictionary · 1913

Veteran

Veteran (vet"ẽr*an) , adjective

[Latin veteranus, from vetus, veteris, old; akin to Greek 'e`tos year, Sanskrit vatsara. See Wether.]

Long exercised in anything, especially in military life and the duties of a soldier; long practiced or experienced; as, a veteran officer or soldier; veteran skill.
The insinuating eloquence and delicate flattery of veteran diplomatists and courtiers. — Macaulay

Veteran (vet"ẽr*an) , noun

[Latin veteranus (sc. miles): compare French vétéran.]

One who has been long exercised in any service or art, particularly in war; one who has had much experience, or has grown old or decrepit in service.
Ensigns that pierced the foe's remotest lines, The hardy veteran with tears resigns. — Addison

In the United States, during the civil war, soldiers who had served through one term of enlistment and had reenlisted were specifically designated veterans.