Boomer

From Memory Alpha, the free Star Trek reference.

"Space boomer" or simply "boomer" is Earth slang for a person who has spent their entire life on spaceships running cargo. Crews of Earth Cargo Service vessels such as the ECS Fortunate and the ECS Horizon would be considered boomers.

Prior to the launch of the NX-01 Enterprise the Humans with the most space experience were boomers, so it is only appropriate that a boomer, Travis Mayweather, be a bridge officer on that ship's historic mission. (ENT: "Broken Bow")