1. The highest level of professional sports competition, particularly in baseball
He finally made it to the major leagues after years of playing in minor leagues.
Ele finalmente chegou à liga profissional após anos jogando nas ligas menores.
2. Any activity or competition at the highest professional or competitive level
Working for that company means you're playing in the major leagues.
Trabalhar para essa empresa significa que você está no nível profissional mais alto.