Definition - What does Vitiate mean?
To vitiate is to ruin or to make void.
In the context of the law, contracts can be vitiated if the terms of the contract are breached, or if one party in the contract does something illegal. Lawsuits can ensue if one party vitiates a contract that it has in effect with another party.
Justipedia explains Vitiate
There are many things that can vitiate a contract. One such scenario is if one party in the contract attempts to defraud the other party, this could vitiate the contract. This could happen if one party attempts to scam or lie to the other party.
For example, if a bottled water company promises a grocery store that it will deliver 1,000 cases of fresh spring water, but instead delivers 1,000 cases of tap water, this could cause the contract to become vitiated. The grocery store may even sue the water company as a result.