The definition of second string refers to someone or something that serves as backup for the top choice.
An example of second string is the quarterback who only gets put into the game after the better quarterback breaks his arm.
- Sports that is the second or a substitute choice for play at the specified position
- subordinate or inferior in rank, importance, etc.
Origin of second-stringsee string,
The group of players that substitute for the starting players or from which substitute players are drawn on a sports team.