When a person is vetted, he or she is investigated fully before being given a particular job, a role, or a position; especially, one that involves military or political secrets.
When US Citizenship and Immigration Services (USCIS) vets immigration applicants, they may not have a clear picture of their backgrounds because their governments may not allow such data to be transferred to another nation.
2. Etymology: from Latin veterinarius, "a doctor who medically treats animals"; to vet was originally a horse-racing term, referring to the requirement that a horse be examined for health and soundness by a veterinarian before being allowed to race; now, it has the general meaning of, "to check, to inspect, to scrutinize".According to drafts of the executive action obtained by CNN, the order bars all persons from Iraq, Syria, Iran, Sudan, Libya, Somalia or Yemen from entering the United States for 30 days and suspends the US Refugee Admissions Program for 120 days until it is reinstated "only for nationals of countries for whom" members of Trump's Cabinet deem can be properly vetted.
The following cartoon shows the meaning of "scrutinize" which is a synonym for "to vet".
