1. To answer for (another); to personally assure (the suspect’s mother vouched for him).
2. To call upon, rely on, or cite as authority; to substantiate with evidence (counsel vouched the mathematical formula for determining the statistical probability).
3. Hist. To call into court to warrant and defend, usu. in a fine and recovery. See FINE(1).
4. Hist. To authenticate (a claim, etc.) by vouchers.