The phrase "former neurosurgeon" means that someone used to be a doctor who specialized in surgery on the brain and nervous system, but they no longer do that job. Full definition
• Doctor Strange — Directed by Scott Derrickson (Sinister), Benedict Cumberbatch is now in negotiations to take on the lead role of a narcissistic former neurosurgeon with mystical powers. (filmcutting.com)
On the Republican side, despite their popularity now, businessman Donald Trump and former neurosurgeon Ben Carson have hit the top of their support and neither is likely to see more gains going forward. (realtormag.realtor.org)
The former neurosurgeon favors a flat tax that resembles a system of biblical tithing. (inc.com)