JOHANNESBURG, South Africa — Barack Obama has become the first sitting US president to perform a real-life subtweet (noun: a post on Twitter that refers to a particular user without directly mentioning them, typically as a form of furtive mockery or criticism), directing his ire at a number of African leaders. 

In an historic address Tuesday at African Union headquarters in Addis Ababa, Obama started off all buddy-buddy, reminding the audience that he is the son of an African. He proceeded to tear repressive governments and leaders a new one — for the most part without naming names. But we knew who he meant.

Like you, AU host government Ethiopia, jailer of journalists and repressor of civil society, with a truly unbelievable 100 per cent win in recent elections.

"Democracy is not just formal elections," Obama noted. "When journalists are put behind bars for doing their jobs or activists are threatened as governments crackdown on civil society then you may have democracy in name, but not in substance."

Or you, Robert Mugabe, nonagenarian president of Zimbabwe and the current AU chairman — though not in attendance for Obama's address.

"Nobody should be president for life," Obama said. "Your country is better off if you have new blood and new ideas."

As for you, Burundian President Pierre Nkurunziza and your third term, Obama just said it straight: "When a leader tries to change the rules in the middle of the game just to stay in office, it risks instability and strife, as we’ve seen in Burundi.

"Sometimes you will hear leaders say 'I'm the only person who can hold this nation together.' If that's true, then that leader has failed to truly build their nation."

This was the first time a US president has addressed the AU, which dates back to 1963 and represents all countries in Africa except Morocco. And possibly the last for a while.