/dih-SUR-tuh-fy/ – verb
Definition: Hủy bỏ chứng chỉ, không công nhận.
A more thorough explanation: to withdraw or otherwise end the certification of something (=formal statement that something is true and correct or that a person can perform a certain job, that something is of a particular quality, etc.)
Example: She made a claim to decertify the results of the November 4 election.