means A person with long experience in something, especially one who has served in the armed forces.

from From Latin veteranus, 'old, experienced,' built on vetus, 'old' — the same root that gives us 'inveterate' and is a cousin of words for years and age. In Roman usage a veteranus was specifically a soldier who had completed long service, so the military sense rode along with the word from the very beginning. It entered English through French in roughly the late 16th to early 17th century, carrying both meanings: the seasoned soldier and, more broadly, anyone grown old in a trade.