It can be translated as the Portuguese Language Museum. It’s a very interesting one, actually. It comprises three floors. When I visited, the first floor was being used for a very interesting exhibition regarding the history of relations between France and Brazil, mostly focused on language interchange.
The rest of the museum is dedicated to the Portuguese language, using a cinema-like room, where the screen suddenly disappears and reveals a passage to a huge circular dark room where you listen to sounds and are surrounded by hundreds of words going from one place to another. It also has special interactive rooms for the kids (curiously enough – or not – the same idea as the Museo del Oro in Bogotá), and a hall with a giant video-wall with images, music and excerpts of interviews with Chico Buarque, Gilberto Gil, etc.
I’ve never been a die-hard fan of museums, but whenever I get good advice, I usually take it.