Definition of unmaster in English:

unmaster

Pronunciation /(ˌ)ʌnˈmɑːstə/ /(ˌ)ʌnˈmastə/

verb

  • To make no longer master; to cause to lose mastery or control.

Origin

Late 16th century; earliest use found in Joshua Sylvester (d. 1618), poet and translator. From un- + master.