turncoat
nounUK /ˈtɜːnkəʊt/
US /ˈtɜːrnkoʊt/
A turncoat is a person who switches to the other side.
The soldiers called him a turncoat after he joined the enemy army.
OTHER MEANINGS
2. Someone who changes their beliefs or opinions to suit themselves.
He was a turncoat who supported whichever team was winning.
3. A person who abandons a group or cause for another.
The club saw him as a turncoat when he left for their rivals.
4. In history, a person who changes allegiance during a conflict.
The turncoat shared secrets with the opposing side.