A pioneer or settler was anyone who was the first to explore or settle in a region. Pioneers were known for their adventurous spirit. (TNG: "Silicon Avatar") As such, it was the name of several space probes and a baseball team.
James T. Kirk's ancestors were American pioneers during the 19th century. When Spock suggested that the Melkot chose the battle at the OK Corral for the USS Enterprise landing party's punishment based upon Kirk's cultural past, Kirk agreed. (TOS: "Spectre of the Gun")
Alternately, the team later applied to a scientist who was one of the first in their field of study. Rose Kumagawa, John Kelly, Neil Armstrong, and John Glenn were also considered space exploration pioneers. (VOY: "One Small Step")
The colonists on Terra Nova were against a second wave of settlers from Earth, as voiced by opposition head Mark Logan in several hostile transmissions. (ENT: "Terra Nova")
Sarah April was known for being a pioneer doctor in space. (TAS: "The Counter-Clock Incident")
As a child, Kathryn Janeway recalled going on backpacking trips with her family. Her parents believed it would help her and her sister Phoebe keep a connection to their pioneer roots. (VOY: "Resolutions")