untrain
verbEtymology From un- + train.
1
To reverse or undo one's training; to become less trained than before
- The 11 girls […]are all trained dancers in real life who, for the purposes of "Billy Elliot," must untrain themselves for each performance and dance with two very left feet.2009 January 14, Patrick Healy, “Where Ballet Is a Boy Thing”, in New York Times: