a person who is among the first to explore or settle a new country or area. 5 days ago · A pioneer is also a person who is among the first to enter and live in an area, esp. Pioneer definition, a person who is among those who first enter or settle a region, thus opening it for occupation and development by others. Pioneer definition is - a member of a military unit usually of construction engineers. Pioneer definition: Someone who is referred to as a pioneer in a particular area of activity is one of the. noun · 'Pioneers swear in fidelity to the Communist Party and Lenin.