back up (2)
Meaning: If you back up what you say, you use evidence or examples to show that it's true.Synonym: support
- back sth up When making a claim, you should be able to use evidence to back it up.
- back up sth They'll back up her story with photos, video clips and witness statements to prove that what she's saying is true.
- back sth up with sth When writing an essay, you should state your main idea and then back it up with supporting evidence.
back up (2): claim, thesis, hypothesis, belief, contention, idea
back up with: evidence, examples, proof
If you accuse someone of doing something wrong, make sure you can back up what you say with