I actually don't know exactly what to say about it, other than it's quite nice; I think it could definitely classify as tea. Anyway, I have two Brazilian students now that have let me enjoy some Chimarrao with them during our classes together. It comes across as just a little grassy and smoky kinda like a good maofeng. It's a little thick in texture, and goes down quite smooth with a pleasant finish that resembles a good, full cooked green tea.
There are many traditions that surround the drinking of Chimarrao in Brazil and South America. Some places drink it with hot water, others cold water, and some places will substitute milk. The thermos should be filled with the Chimarrao powder/tea over the brim and packed down. Then a metal straw called a bomba is inserted and slid down to the bottom of the thermos. The water (boiling or cold...or milk) is poured down into the front wide-mouthed thermos and passed with the left hand (closer to the heart?) to one person to drink. The drinker should finish that portion, usually not so much to drink, and then fill it with water and pass it off to the next person. Anyway, this is how we drank it during class.
Not really sure what else to say except to google Chimarrao (or Mate in Spanish). I found this link with some pictures for you folks to check out:
If you get the chance, make sure you try some of this. It's quite nice!