Yeah, means vertical in Japan, rhymes with Latte I think. Lots of people just say tate to rhyme with mate though, and use it in phrases like 'tate the monitor, so I don't think it really matters here.
It's a Japanese word (縦) which means vertical, so it's often pronounced the Japanese way: Ta-Te.
I used to think it was short for ro-tate myself, so I still call it that in my head