I just answered this question at the Multilingual Mania Facebook page and it started me thinking. My answer was:
"To me it means being a part of two separate worlds defined by the two languages, and belonging to them both. It's a constant challenge and a game of deep undercover, with points scored when I make a good turn of phrase or someone believes I'm a native speaker, and points lost when I lose my cover by making a silly mistake. These are the things that keep my life interesting from day to day :)"As I've written about before, for me it's less about being two people or having two personalities and more about being one person who moves between two worlds. I think this one is key for me.
And the challenge...I do love a challenge, and this one hasn't gotten old so far. I remember my first year after university (after coming back from a three month stay in Prague) I had a job and an apartment and absolutely no challenge in my life. I was bored stiff. I read a huge number of books that year, difficult, challenging books that made me think, because I needed to use my brain. That was part of the appeal of moving to a new country and learning a new language: at first, even (especially!) grocery shopping is a challenge! I thrive on it, and I still get bored if things start getting too easy.
Along with the challenge, I love the undercover agent game aspect. I have two names (CZ/SK surnames are slightly different for women), two identity cards, two marriage licenses. I'm not quite what I seem. Still no numbered Swiss bank account or Q to give me gadgets, but it's still pretty awesome.
But then I realize, those are pretty much the same answers I could have given six or seven years ago. They relate just to me in relationship with the society around me. But they don't take into account how I've changed since then. They don't account for love, for my husband, for my daughter.
So to me, bilingualism also means love. It means I can tell my husband I love him in his own language. It means when he retreats into his own language, in laughter, in pain, in stress, in pleasure, I can follow him there. When he wants to share with me a joke or a movie from his childhood, I can appreciate it. It means I come into his world. And all of this applies equally for him to me.
Then when it comes to our daughter, bilingualism means that she is connected to her family, her extended family, generations of Slovaks and generations of Americans stretching back into the past, and the cultures that produced us all. She can share the songs, the movies, the customs, the food of both sets of grandparents. It means she has two whole worlds open to her...just as a start. Bilingualism means I serve as her interpreter when she needs one - not her as mine.
It means I can have a relationship with my in-laws, and help my daughter to do the same. It means I can support my husband when he forgets a word, my daughter when she doesn't know one.
Bilingualism makes my family possible. And you don't get any more essential than that.