Brain fever and Meningitis

Brain fever noun - Meningitis caused by bacteria and often fatal.

Meningitis and brain fever are semantically related. In some cases you can use "Meningitis" instead a noun phrase "Brain fever".

Meningitis noun - Infectious disease characterized by inflammation of the meninges (the tissues that surround the brain or spinal cord) usually caused by a bacterial infection; symptoms include headache and stiff neck and fever and nausea.

Brain fever and meningitis are semantically related. You can use "Brain fever" instead a noun "Meningitis".