I am reading Zerocalcare, and I am stuck at this word.
http://www.zerocalcare.it/2018/10/09/quando-i-vecchi-salgono-nella-tua-macchina/
Third picture from top, the male character responds to his mother's comment on how dirty his car is, by saying:
"La macchina è mia e la tengo come cazzuccio mi pare a me, va bene?".
What does this mean? I am guessing "cazzuccio" is a rude word, but I can't find it anywhere. I have tried the Collins dictionary, the Oxford dictionary, and Wiktionary.
The standard Italian sentence (low, colloquial register) would be
La macchina è mia e la tengo come [cazzo] mi pare a me, va bene?
The car is mine, and I keep it (how I [fucking] like / how [the fuck] I want), is that fine?
As noted in the comments and in the other answer, cazzo is used as a generic expletive, like fucking in English. It is idiomatic to add it without prepositions after come or other interrogative pronouns, exactly like the fuck is used in English.
Note that another expression that is grammatically incorrect in textbook Italian but common in the low/popular register is mi pare a me: grammar rules would dictate that either mi or a me is used, but not both.
The 'endearing' version cazzuccio is non-standard usage; the author used it as a literary device for comic effect here. He is mixing registers for comic effect: those sentences pair a fake exaggeratedly polite / endearing tone with a couple of very vulgar / impolite expressions to invite her not to bother him. See also cariiisssima madriiisssima earlier, where the same fake polite tone is used. Literally it means my dearest motherest: madrissima is another made-up word, where a superlative ending is added to a noun instead of to an adjective. The supernumerary repeating i's and s's are used to show in writing that these words are spoken out slowly, to add emphasis.
Overall this is a very difficult text to read for a non-native speaker. The author uses literary devices, made-up or uncommon words, expressions from the youth slang and Roman dialect, popular culture references.
The term cazzuccio is an endearing (as correctly specified by @Denis Nardin) term of cazzo, which is a rude word.
The literal meaning of cazzo is a vulgar term for “penis” (“cock” say), but it is used as a kind of universal expletive, not dissimilar from “fuck” (and “fucking” etc. ) in English.
It also means that the person who’s speaking has some confidence with the other person and doesn’t want to hurt his or her feelings.
And yes, the sentence just mean:
The car is mine and I keep it like sh*t looks to me. (Don’t bother me with your rants.)
Moreover, about the suffix -uccio (as suggested by @Charo):
-ùccio [lat. -ūceus] (f. -ùccia; f. pl. -ucce). – 1. Suffisso che serve a formare sostantivi e aggettivi alterati con valore diminutivo, di tono ora vezzeggiativo ora, e più spesso, spregiativo: tesoruccio, casuccia, guadagnuccio, gentuccia (gente meschina), robuccia (roba scadente), ecc. 2. Come agg., nel linguaggio fam., misero, scadente: un affaruccio uccio uccio; questo vestito si è fatto un po’ uccio, si è un po’ logorato.
Cazzuccio is, indeed, the "endearing" form of cazzo (by adding the endearing suffix -uccio), used as an emphatic and also to somewhat reduce the aggressivity of the response, since the author is speaking to his mother.
The opposite effect would have been obtained with an augmentative prefix - "La macchina la tengo come stracazzo mi pare".
It translates well enough to "I'll keep my car like I jolly fucking want", at least in British English, as the "rude" form of jolly well:
informal•British
used for emphasis, especially when one is angry or irritated. "I'm going to keep on eating as much sugar as I jolly well like"
Charo is correct, however, in saying that it normally would have a pejorative meaning - that's because the endearing terms (at least in Italian) usually also imply a smaller size, power, or duration than average: tesoruccio is a little treasure, endearing when it's a child, but obviously disappointing when it's loot.
