If you have an exposed pipe in a basement, you can wrap it with self-regulating heat tape. Plug it in and let the thermostatic technology do the work.
Congratulations (or rather, condolences), you likely have a frozen waste pipe.
In many homes, a waste pipe freezes because cold air is blowing around the pipe. Check for holes in the siding or foundation where the pipe exits. Fill those gaps with spray foam.
A frozen waste pipe is a race against the clock. Act fast, use gentle heat, and never let desperation drive you to a flame thrower. Stay warm, and good luck un-gunking those pipes