Yes, it was a brute force attack. Apples now trying to cover it up by claiming "If only you had a better password." Which may be true, if their passwords had been 50 characters long it would have taken the brute force attack a lot long to complete. But the fact of the matter is, Apple forgot to put in an X number of wrong attempts = account locked, procedure in... or it wasn't working properly and people exploited it.
In cryptography, a brute-force attack means that you don't know anything about the password, but just try all the billions of possibilities. Assuming that a password character can only be a-z, A-Z, 0-9, and 10 other characters, and assuming that a password has exactly 6 characters, you would have to try on average (72^6)/2=69657034752 passwords. Assuming you can do 100 tries per second, that would still take more than 8062 days, or more than 22 years on average. Note that I'm being very generous in my assumptions here.
In other words, unless there was another weakness, a brute-force attack was impractical, even without any limit on the number of attempts.
What probably happened was that the passwords were indeed weak. If you know your victim has a dog called 'fido', you can try if she used that name in her password, and in my example you only have to guess two more characters. That only takes seconds or minutes. The attackers may call this brute force, but that's misleading.