In the episode "Bête Noire", Ducky says the word stat, which is a medical term, to alert the team that he was being held hostage. But Ari is a pathologist. It makes no sense that he didn't notice that Ducky was alerting Gibbs that he was in danger.

It was sort of a round about way for Ducky to raise the alert. STAT is the term for a medical emergency. Techincally there's no such thing as a medical emergency in autopsy because all the patients are dead.

GIBBS: Autopsy. TV. Now! Why would Ducky say STAT?
ABBY: Because he’s a doctor? And because STAT means fast and a medical emergency?
GIBBS: (OVERLAP) Medical emergency. But what is a medical emergency in autopsy?

Ari didnt realise that Ducky was alerting Gibbs, because although he is a pathologist he doesn't know that it is abnormal for Ducky to use a term like stat. for all Ari knew he could have used it everyday

it was a code