[makh-kair-RON-ikko] “Maccaroni-ish”. This is the term Italians themselves use for heavily Italianized and very poor English. Not rude, except to the person/discourse to whom you are applying it.
Madonna, Madonna Mia
[mah-DON-na MEE-a] My Madonna! A general exclamation of shock, can be used in polite company.
[MAHM-ma MEE-a] My mom! General exclamation of shock or consternation, similar to Madonna mia. Yes, it’s cliché, but it really is used in Italy.
Mandare all’inferno, a quel paese
[mahn-DAH-ray ahl in-FAIR-no, ah quell pah-AY-zay] To send to hell or to that place – to tell someone to go to hell. Inferno wouldn’t be considered particularly rude today, but mandare a quel paese survives as an alternative, a relic of when wishing someone to hell was very rude indeed.
[mahn-NAHJ-jah] The word itself is very mild, equivalent to drat or darn. But it can be quite satisfying if you really spit it out.
[mar-PYOH-nay] Skirt-chaser, a man constantly trying to seduce women. The term makes no judgement as to his eventual success. Related to furbo.
[may-nay-fray-GHEES-ta] From me ne frego – Someone who doesn’t care.
[MARE-dah] noun – Shit, though not used nearly as often as in American English. Except in Siamo nella merda – “We’re in the shit.”
Mettere le Corna
[MET-ter-ray lay COR-na] To put horns on (someone else) – to (sexually) betray one’s spouse. Hence cornuto. Not particularly rude when used in this way, e.g. Non sa che sua moglie gli mette le corna con il macellaio – “He doesn’t know his wife is cheating on him with the butcher.” (I chose the butcher as an example, not because I know of any specific cases, but because butchers are popularly supposed to be getting a lot of it – dunno why, perhaps the proximity to all that meat?)
[mean-YOT-tah] Prostitute. Used in the exclamation Porca mignotta!
[MINK-ya] Sicilian slang for penis. Used as an exclamation: Minchia!
[MIN-nay] Tits. I think this originates in Tuscan dialect.
[mee VAH] This is slangy but not particularly rude. Literally it means “it goes me,” (mi – reflexive pronoun for myself, va – from the verb andare, to go) but it’s used for “I like it” with a verb, as in Non mi va di… – “I don’t want to do… ” Also used for something else you do or don’t like: Mi andrebbe una bella bistecca stasera: “I’d really like a good steak this evening.”