Today’s word of the day, boia, traditionally means an executioner or a hangman. Colloquially, it means nothing of the sort.
One uses boia to express abundance, usually to refer to either very cold or very hot weather. However it can also be used to say great … anything.
Examples:
‘Fa un caldo boia a Roma.’ – It’s super hot in Rome.
‘Questo mal di gola mi fa un male boia!’ – This sore throat hurts like hell.
The term is used to “enlarge” negative things to the point that they “could kill you”, hence the link with the executioner. “Un caldo boia” is so hot that it could kill you, “una fame boia” makes you so hungry that it could kill you, etc etc. It’s used almost exclusively to emphasize negative factors. You can swap it with “della Madonna” in many cases, although that’s technically blasphemous and more of a northern thing.
Note also the sentence “boia chi molla”, which was a fascist shout to “keep fighting” — it’s sporadically used in right-wing circles, especially around Rome.