Meaning of backup:
a person or thing that supports or reinforces another.
Synonym for backup:
1. assistant:a person who assists or gives aid and support; helper.
2. aid: to provide support for or relief to.
3. help: to give or provide what is necessary to accomplish a task or satisfy a need; contribute strength or means to; render assistance to; cooperate effectively with.
4. support: to bear or hold up, to sustain or withstand.
5. reinforcements: the act of strengthening with some added piece, support, or material.
6. reserves: to serve again.
7. affirm:to state or assert positively; maintain as true.