Oh, ok. I don't know the word in English but maybe I can help. In Mexico, an "asignatura de arrastre" is one from an earlier semester which you haven't passed. So, if I'm in third semester, but I haven't passed, say "Math II" from second semester, then "Math II" is an "asignatura de arrastre".
A "resit exam" is something we would call "examen de regularización". And it might be one way to pass that "asignatura de arrastre", but there might be other options, so I wouldn't say "resit exam" is a perfect translation for "asignatura de arrastre".
I hope that helped.
