Source : Webster's Revised Unabridged Dictionary (1913)

Obligate \Ob"li*gate\, v. t. [imp. & p. p. {Obligated}; p. pr. &
   vb. n. {Obligating}.] [L. obligatus, p. p. of obligare. See
   {Oblige}.]
   1. To bring or place under obligation, moral or legal; to
      hold by a constraining motive. ``Obligated by a sense of
      duty.'' --Proudfit.

            That's your true plan -- to obligate The present
            ministers of state.                   --Churchill.

   2. To bind or firmly hold to an act; to compel; to constrain;
      to bind to any act of duty or courtesy by a formal pledge.

            That they may not incline or be obligated to any
            vile or lowly occupations.            --Landor.

Source : WordNet®

obligate
     adj : restricted to a particular condition of life; "an obligate
           anaerobe can survive only in the absence of OXYGen"
           [ant: {facultative}]

obligate
     v 1: force or compel somebody to do something; "We compel all
          students to fill out this form" [syn: {compel}, {oblige}]
     2: commit in order to fulfill an obligation; "obligate money"
     3: bind by an obligation; cause to be indebted; "He's held by a
        contract"; "I'll hold you by your promise" [syn: {oblige},
         {bind}, {hold}]