Loosely translated = "How appalling!"
Loosely translated = "Who cares?"
(Yes, I see that I've misspelled it. Thbbbt!)
Most of my own outlook on life can be summed up using the same two words.
If, by chance, you are actually searching for what #tbt means, that stands for "ThrowBack Thursday". You'll see that on Facebook a lot when people post old photos.