can trigger override validation rules in Salesforce?

It is not possible for triggers to ignore validation rules without adding custom logic. If the request to save a record originates outside of a Standard UI edit page, any before triggers you've defined will run prior to the execution of validation rules.
Here is strategy to bypass this behavior:
1. Add a "Skip Validation" Checkbox field to the object
2. Set the "Skip Validation" field to TRUE in a before trigger.
3. Add logic to your validation rules so that they do not execute if "Skip Validation" is set to TRUE.