1. To hang on to something with extreme grip.
2. To be left waiting (hanging), sitting at a standstill while you await the return of someone.
3. When you are in a hurry but need something badly, and another person is going to help you out, but all they can do at the moment is tell you to "hang tight"
OJ: I'll take that large bag of smelly sticky bud there.
Drug dealer: ok that will be $60
OJ: Hands him a hundred dollar bill and ask for change.
Drug dealer: Hang tight yo, i'll be right back
While getting it on with your girl she says where is your condom, you reply, ill go get one, hang tight yo!