Definition of "forerunner"

forerunner

noun
plural forerunners
1. A runner at the front or ahead.
2. (sports) By extension, a non-competitor who leads out the competitors on to the circuit, or who runs/rides the course prior to competitor trials, usually testing or checking the way.
3. A precursor or harbinger, a warning ahead.
  Quotations
  How meek and shrunken did that haughty Tarmac become as it slunk by the wide circle of asphalt of the yellow sort, that was loosely strewn before the great iron gates of Lady Hall as a forerunner of the consideration that awaited the guests of Rupert, Earl of Kare, […] .
  1922, Michael Arlen, “3/1/1”, in “Piracy”: A Romantic Chronicle of These Days‎
  Acute infections of the female urethra, which are the forerunners of chronic infections, may be initiated by a number of conditions: Traumatism due to difficult labor, presence of foreign bodies such as calculi, […]
  1951 January, Gordon W. Reynolds, “The Female Urethra and Chronic Urethritis”, in Northwest Medicine, volume 50, number 1, Portland, Ore.: Northwest Medical Publishing Association, page 33
  On December 22, 1974, a swarm of earthquakes, the largest event being of magnitude 4.8, occurred 70 km northeast of Haicheng. All these phenomena were considered the forerunners of the major event. Thus, in January 1975, another SSB conference offered a short-term prediction that an earthquake of magnitude 5.5–6 would occur in the Yingkou-Luda-Tantung area in the first six months of 1975 (HESD, 1977).
  1985, Shiu-hung Luk, “Management of Earthquake Hazard: The Program of Earthquake Forecsting in China, 1966–1976”, in China Geographer Number 12: Environment‎, published 2018, page 10
4. A forebear, an ancestor, a predecessor.
5. (philately) A postage stamp used in the time before a region or area issues stamps of its own.