Source : Webster's Revised Unabridged Dictionary (1913)

Undertake \Un`der*take"\, v. t. [imp. {Undertook}; p. p.
   {Undertaken}; p. pr. & vb. n. {Undertaking}.] [Under + take.]
   1. To take upon one's self; to engage in; to enter upon; to
      take in hand; to begin to perform; to set about; to
      attempt.

            To second, or oppose, or undertake The perilous
            attempt.                              --Milton.

   2. Specifically, to take upon one's self solemnly or
      expressly; to lay one's self under obligation, or to enter
      into stipulations, to perform or to execute; to covenant;
      to contract.

            I 'll undertake to land them on our coast. --Shak.

   3. Hence, to guarantee; to promise; to affirm.

            And he was not right fat, I undertake. --Dryden.

            And those two counties I will undertake Your grace
            shall well and quietly enjoiy.        --Shak.

            I dare undertake they will not lose their labor.
                                                  --Woodward.

   4. To assume, as a character. [Obs.] --Shak.

   5. To engage with; to attack. [Obs.]

            It is not fit your lordship should undertake every
            companion that you give offense to.   --Shak.

   6. To have knowledge of; to hear. [Obs.] --Spenser.

   7. To take or have the charge of. [Obs.] ``Who undertakes you
      to your end.'' --Shak.

            Keep well those that ye undertake.    --Chaucer.

Undertake \Un`der*take"\, v. i.
   1. To take upon one's self, or assume, any business, duty, or
      province.

            O Lord, I am oppressed; undertake for me. --Isa.
                                                  xxxviii. 14.

   2. To venture; to hazard. [Obs.]

            It is the cowish terror of his spirit That dare not
            undertake.                            --Shak.

   3. To give a promise or guarantee; to be surety.

            But on mine honor dare I undertake For good lord
            Titus' innocence in all.              --Shak.

Source : WordNet®

undertake
     v 1: enter upon an activity or enterprise [syn: {set about}, {attempt}]
     2: accept as a challenge; "I'll tackle this difficult task"
        [syn: {tackle}, {take on}]
     3: promise to do or accomplish; "guarantee to free the
        prisoners" [syn: {guarantee}]
     4: enter into a contractual arrangement [syn: {contract}]
     5: accept as a charge [syn: {take in charge}]
     [also: {undertook}, {undertaken}]