What Splodge said.
But does infantry carrying capacity disqualify from Tankdom? The Merkava has a troop carrying capacity and it is a tank. Of course troop carrying isn't its primary role.
The problem with that dictionary definition is that there are a number of tanks that don't possess cannon at all just machine guns (PzI, Matilda, Great Wat British female tanks). It would also classify a number of self propelled guns as Tanks and that's just wrong.
I would like to add the both Stugs and Universal carriers are cool as f*ck they just aren't tanks 😝