泯 is a bound classical character, almost never standalone. You'll meet it in fixed phrases like
良心未泯 (liángxīn wèi mǐn, 'conscience not yet extinguished') and
童心未泯 (tóngxīn wèi mǐn, 'still has a child's heart'), and in compounds
泯灭 (mǐnmiè, to be obliterated) and
泯没 (mǐnmò, to vanish).