Any of the several models of the ThinkPad laptop computer, manufactured first by IBM and later by Lenovo. So called because of its black color and simple rectilinear appearance. Regarded as efficient, reliable, sturdy for a laptop, and relatively economical. Ubiquitous in business.
My old Dell died, so I bought a basic black brick, a slightly used IBM T-41, and I'm happy with it. It's not hi-res, I wouldn't use it for anything fancy, like online gaming. But it works well with WiFi, it gets my work done quickly and smoothly with very little trouble, and it only cost me $500.