멋대로 + verb (멋대로 하다); 제멋대로 = as one pleases
as one pleases, at will, selfishly
Example
남의 물건을 멋대로 쓰면 안 돼요.
You shouldn't use other people's things as you please.
Word parts
멋 'one's own taste' + 대로 'as, according to'.
Good to know
Negative tone; 마음대로 is the neutral 'freely, as you like'.
Related words