The :g command can be used to execute an Ex command over the entire buffer for all lines that match a given pattern. By choosing d (delete) as the Ex command, all lines that match the given pattern will be deleted. For instance, if I want to remove all lines that contain binding.pry, I can execute the following command:

:g/binding\.pry/d

See :h :g for more details.

h/t Chris Erin