It is a typical slang word meaning
man. It could be used as a derogatory form of naming a
person.
But, in some situations, it could be interpreted as a very masculine man, one that a
woman is attracted to.
Negative: "ese lo que es es un macharran" - "that
guy is just an
asshole"
Positive (from
woman to a man she likes): "lo que necesito es un macharran como ese que me caliente por las noches" - "what i need is a man like that to keep me warm at night"