Túnel is a tunnel, obviously.
Tunelar is "to drill tunnels". I am not sure it was standard Spanish (now, post Ruiz-Gallardon, it is!).
Tuneladora is "she who drills tunnels". This is because máquina is of the feminine grammatical gender in Spanish.
By analogy, a drill is taladro or taladradora (a drill bit is not taladro but broca, don't ask me why). Taladrar means to bore a hole. So, TBM does translate as taladradora, but those are hand-held so I suppose it's good they came up with a new term.
Another word for "boring holes" is trepanar, and trépano is the instrument used.
"Hole boring" can also be translated as aburrir a los agujeros, but that's just a snark. Most economists teach a theoretical framework that has been shown to be fundamentally useless. -- James K. Galbraith
