The Collaborative International Dictionary of English v.0.48:

Mandatary \Man"da*ta*ry\, n. [L. mandatarius, fr. mandatum a
   charge, commission, order: cf. F. mandataire. See Mandate.]
   1. One to whom a command or charge is given; hence,
      specifically, a person to whom the pope has, by his
      prerogative, given a mandate or order for his benefice.
      --Ayliffe.
      [1913 Webster]

   2. (Law) One who undertakes to discharge a specific business
      commission; a mandatory. --Wharton.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mandatary
    n 1: the recipient of a mandate [syn: mandatary, mandatory]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

MANDATARY, contracts. One who undertakes to perform a mandate. Jones' Bailm.
53; Story on Bailm. 38. Dr. Halifax calls him mandatee. Halif. Anal. Civ.
Law, 70, Sec. 16, 17.
     2. It is the duty of a mere mandatory, it is said, to take ordinary
care of the property entrusted to him. Vide Negligence. But it has been held
that he is liable only for gross negligence. 14 S. & R. 275; 2 Hawks, R.
145; 2 Murph. R. 373; 3 Dana, R. 205; 3 Mason, R. 132; 11 Wend, R. 25;
Wright, R. 598; 1 Bouv. 1st. n. 1073.