1. Members of a group, team, or organization who are available to substitute for primary members when needed
The backup members of the football team practiced regularly to be ready for any game.
Os membros de reforço do time de futebol treinavam regularmente para estar prontos para qualquer jogo.
2. Reserve personnel who support the main staff or roster
The company hired backup members for the project to ensure continuity.
A empresa contratou membros de reforço para o projeto para garantir continuidade.