What do the Dutch academic titles "prof.dr.dr.h.c.ir." mean?
Here you go:


prof is short for professor.
dr is short for doctor, which signifies either MD or PhD.
dr. h. c. stands for doctoratus honoris causa, which is an honorary title.
ir stands for engineer (ingenieur).


In this case it means a professor (with a PhD) with an engineering background, who got an honorary title at some point.