What do you call slapping someone at the back of their head

That was referred to as "slapping or smacking someone upside the head" when I was growing up. It's described here in this comedy video by Chris Rock where a disgruntled doorman starts smacking people upside the head - always with an upward motion of the hand and usually on the back of the head.

This New York Times article talks about this expression as having started as one used by blacks and then adopted by all races in the southern part of the United States. I went to high school in a racially mixed region of the US and heard this expression frequently.

Dope slap is the most common expression I know for striking someone in the back of the head with an open palm. The b-expression, which I will not repeat, usually refers to a different kind of strike, typically a backhand across the face (or am I thinking of the pimp slap?).

seftie or sefty Australian slang for a open handed slap up the back of the head