untrain

un- +‎ train

untrain (third-person singular simple present untrains, present participle untraining, simple past and past participle untrained)

1. To reverse or undo one's training; to become less trained than before
   • 2009, January 14, “Patrick Healy”, in Where Ballet Is a Boy Thing‎:

     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.

• urinant