Proprio is one of those words you encounter in Italy a dozen times a day. You might see a gelateria advertizing its “produzione propria”, for instance, or hear someone agree with you that “è proprio così”.
The various meanings might seem slippery when you first try to grasp them, but I promise they all make sense.
Let's start by looking at what the word reminds you of in English. Proprio – it sounds a lot like 'proper', doesn't it? And that is indeed one of the ways you can translate it: as an adjective that means 'appropriate' or 'fitting'.
È importante usare il termine proprio.
It's important to use the proper term.
Non è questa la sede propria per parlarne.
This isn't the proper place to discuss it.
But there's another English that proprio brings to mind: 'proprietary'. Like that term, proprio suggests that something belongs to you, that it's all your 'own'.
L'ho visto con i miei propri occhi.
I saw it with my own eyes.
Ogni automobile ha la propria targa.
Every vehicle has its own number plate.
di produzione propria
made in-house (literally: of own production)
In fact proprio can be used to described things that are so much your own that they pretty much sum you up – like the traits that are 'characteristic' or 'typical' of you.
Il clima umido è proprio di questa regione.
A wet climate is typical of this region.
What's really handy is that, like 'own', proprio can be used like a possessive pronoun, to stand in for a noun that you don't want to repeat (just remember to give it the same gender as the word you're replacing).
Se dai la tua approvazione anche gli altri daranno la propia.
If you give your approval, the others will give theirs (or: their own).
Indeed, proprio can be used in many of same ways we say 'own' in English, including as a noun.
Ognuno si prenda il proprio.
Everybody take their own.
Lavoro in proprio.
I work on my own (i.e. for myself, independently).
Ho una casa in proprio.
I have a house of my own.
So far, so consistent. But there's another way to use proprio: as an adverb.
And here's when the meaning changes somewhat, to 'exactly'…
È andata proprio così.
That's exactly how it went.
Exactly! Or: Just like that!
… or 'really' and 'truly'…
Mi ha fatto proprio piacere incontrarti.
It was truly a pleasure to meet you.
Era proprio lui!
It was really him!
… or just to reinforce what you're saying, whether it's positive or negative.
Non mi piace proprio.
I really don't like it at all.
Grazie, ho proprio mangiato abbastanza.
Thank you, I've really had enough to eat.
Mi ha telefonato proprio ora.
She called me just this minute.
Proprio in this last sense is sort of the equivalent of 'really' in English, which explains why you hear it quite so much. You can really (!) add it to anything… and I do mean anything.