Earlier quoted context omitted.
No, a tariff is indeed a tax a country imposes on goods entering its borders. I'm not sure what in my comment you think contradicts this.
> The ships being seized are doing things like flying false flags, to try and trade with Cuba without paying tariffs.
I can see how this wording makes it sound like the US is charging a tariff on the oil entering Cuba, but that is not the case. The tariff in that quote is referring to the tariffs the US is promising to place on counties that don't participate in the embargo.