Indiscriminate f-word usage isn’t usually a good thing for a newcomer to try (just ask Jenny Slate). But when you’re Christian Siriano and the f-word in question is “fierce,” it happens to mean very good things indeed. Along with collaboration deals with big name brands such as Payless and Victoria’s Secret, the 23-year-old designer hailed by Tim Gunn as the next Marc Jacobs has produced four collections under his own label since becoming the youngest winner of Project Runway during the show’s fourth cycle. And while the aforementioned accomplishments no doubt have more to do with Siriano’s design talent than his catchy vocabulary, his latest work has everything to do with his signature pet phrase.

Siriano’s first book. Fierce Style: How to Be Your Most Fabulous Self hit shelves last week, and on Tuesday, he’ll be making a stop in San Francisco to sign copies for fans at Saks Fifth Avenue. We caught up with Siriano before his appearance for a quick chat about fierce style, fashion and his hair cut.

What is fierce style all about?

Inside the book I try to define, obviously, what people ask me everyday, “What is fierce style?”  And I really wanted the book to be not a guide, but my idea of how you can have personal style and have a signature style. It’s about being confident within yourself. In the book, it’s my whole story of finding myself. The idea is that it’s something that you have that makes you stand out from other people. It’s a very personal feeling. It’s the old story of you have to love yourself first. My style, I wouldn’t per se call it fierce until I was a little more experimental.

When did you discover your own fierce style?

I started young. I was 13- or 14-years-old, working at this salon. It was trendy and everybody was so eccentric and so different, and for high school I went to art school. I was in plays and theater and all that.

Your book includes fashion do’s and don’ts – can you share a few with us?

I mean everything is very subjective, but like I think people should dress up and not down. I have things like [don’t do] hoodies, and shapeless denim and big oversized logos and big polyester fabrics.

For me it’s all about getting dressed and how to have this fierce personal style. But I didn’t want the book to be a complete guide, like this is what you do. In the book, I have these chapters like learn from the pros, like watching celebrities and emulating them. I think that’s a great way to learn about fashion.

Who cuts your hair?

I do it myself. No salons. I can’t be bothered.

You’re known for making “fierce” a ubiquitous catchphrase. Are there any new words or phrases you’re obsessed with these days?

I still say, “fabulous,” and, “flawless,” and, I say, “J’adore,” a lot and, “that’s genius,” and, “major,” but nothing too exciting.

Since becoming the youngest winner of Project Runway, you’ve teamed up to launch a makeup line with Victoria’s Secret, shoes with Payless, a phone for LG, not to mention creating your own collections. And now you’ve written a book. So what’s next for you? What other types of product lines would you eventually like to work on?

Payless has been the biggest project. That’s in stores now and people can actually go by them, so that’s exciting. But I‘m not really doing any more collaborations for right now.

You’re involved with so many projects, we’d be surprised if you ever had a day off. Do you?

No, I don’t really have a day off, and I never really have breaks. At least what’s great is I’m not sitting at a desk all day. And it is fun, and it is a dream, and I love doing it.

But if you did happen to have one, how would we find you spending it?

I wouldn’t do anything. I would literally sit at home and watch bad TV all day long. I’d watch the Housewives all day long.

When you’re in San Francisco, do you have any free time to get out and about?

No, I’ll literally be there for that day. And the next morning, I fly early to Los Angeles to do a lot of press, like Chelsea Lately. It’s a quick trip. But it will be fun, and I think it will be interesting. I love San Francisco. I was there about a year ago.

What did you do on your last visit?

It was an appearance at Supperclub. It was really fun….I always come in for like a day.

Want to meet Christian Siriano in person? He’ll be signing copies of his book during an appearance at Saks Fifth Avenue on Tues. Oct 13 from 2-3 p.m. Space is limited. RSVP to 415-438-5411.