noun, masculine/a.vɑ̃.ku.ʁœʁ/plural: avant-coureurs
messenger, scout (person who runs ahead of the army to deliver news); harbinger, precursor, forerunner (thing that foreshadows or foretells the coming of something)
Synonyms: éclaireur
From courir (“to run”) + avant (“in front, before”). Compare English forerunner, precursor.