(usually used in negative sentences) to get involved with sb/sth that may be harmful :
I wouldn't mess with him if I were you.
(usually used in negative sentences) to get involved with sb/sth that may be harmful :
I wouldn't mess with him if I were you.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005