Both jisho.org and Wikipedia have ドットマトリクス for dot matrix (printer), but I've tried using it on a couple of middle-aged people and they didn't understand it. Maybe I've mispronounced it, or overestimated people's ages, or their ability to know computer terminology, but is ドットマトリクス correct, or should I be using something else?
ドットマトリクス is an established word, but unfortunately only among mechanical engineers. I'm not very sure how common the word is in English, but I can confirm that it's anything but what you'd hear from lay people in Japan.
If you want them to grasp the concept of dot matrix, I think you can only explain it: 電光掲示板のような, 古いレシートのような, 絨毯の織り目のような, 点描画のような, 点を並べて作る etc. according to what they're familiar with.
Just did some poking around on the net and my colleges here at work agree, if you are just wanting to talk about Dot-Matrix Printers then use ラインプリンター(Line Printer)
As for Dot-Matrix screens... I don't know, maybe just 昔の液晶画面