Dressing or having a hairdo like an old person. A relatively young person dressed too old. May also be spelled as mert or myrt. Example: I just had my hair done at the hairdressers, and I think it looks a bit mirt. OR Here comes mirt walking down the street.
MIRT
Meaning of MIRT in English
Slang English vocab. Английский сленговый словарь. 2012