take on

1.  Undertake or begin to deal with, as in I took on new responsibilities, or She took on too much when she accepted both assignments. [Early 1300s]
2.  Hire, engage, as in We take on extra workers during the busy season. [Early 1600s]
3.  Oppose in competition, as in This young wrestler was willing to take on all comers. [Late 1800s]
4.  Display strong emotion, as in Don't take on so. [Colloquial; early 1400s]
5.  Acquire as, or as if, one's own, as in He took on the look of a prosperous banker. [Late 1700s]

Definition: assume, accept
Antonyms: refuse, reject

The verb has 6 meanings:

Meaning #1: take on a certain form, attribute, or aspect
  Synonyms: assume, acquire, adopt, take

Meaning #2: take on titles, offices, duties, responsibilities
  Synonyms: assume, adopt, take over

Meaning #3: accept as a challenge
  Synonyms: undertake, tackle

Meaning #4: set about dealing with
  Synonym: tackle

Meaning #5: admit into a group or community
  Synonyms: accept, admit, take

Meaning #6: contend against an opponent in a sport, game, or battle
  Synonyms: meet, encounter, play