take care

1.  Be careful, use caution, as in Take care or you will slip on the ice. [Late 1500s]
2.  Good-bye, as in I have to go now; take care. This apparent abbreviation of take care of yourself is used both orally and in writing, where it sometimes replaces the conventional Sincerely or Love in signing off correspondence. [Colloquial; 1960s]

The verb has 3 meanings:

Meaning #1: be careful, prudent, or watchful

Meaning #2: be in charge of or deal with
  Synonym: mind

Meaning #3: take charge of or deal with
  Synonyms: attend, look, see