[noun] [U] UK humorous - a stupid person, often used to describe yourself when you have done something silly or when you feel you are being treated unfairlyI suppose muggins (here) will have to look after the cat when they go on holiday (= I will have to do it but I don't want to).
MUGGINS
Meaning of MUGGINS in English
Cambridge English vocab. Кембриджский английский словарь. 2012