means a person who is among the first to explore, settle, or develop something — a place, a field, a technology — clearing the way for others to follow.

from From Old French 'peonier,' a foot soldier — and not the glamorous kind. These were the laborers of the army, sent ahead to dig trenches, build bridges, and clear roads before the main force arrived. The root is 'peon,' meaning a foot soldier or pawn (ultimately from Latin 'pes,' foot — a cousin of 'pedestrian' and 'pawn'). So the pioneer was literally the one walking out front with a shovel, doing the dangerous groundwork. Only later did the word climb in status to mean any bold first-mover.