honorarium
    n 1: a fee paid for a nominally free service

Honorarium \Hon`o*ra"ri*um\, Honorary \Hon"or*a*ry\, n. [L.
   honorarium (sc. donum), fr. honorarius. See Honorary, a.]
   1. A fee offered to professional men for their services; as,
      an honorarium of one thousand dollars. --S. Longfellow.
      [1913 Webster]

   2. (Law) An honorary payment, usually in recognition of
      services for which it is not usual or not lawful to assign
      a fixed business price. --Heumann.
      [1913 Webster]

HONORARIUM. A recompense for services rendered. It is usually applied only 
to the recompense given to persons whose business is connected with science; 
as the fee paid to counsel. 
     2. It is said this honorarium is purely voluntary, and differs from a 
fee, which may be recovered by action. 5 Serg. & Rawle, 412; 3 Bl. Com. 28; 
1 Chit. Rep. 38; 2 Atk. 332; but see 2 Penna. R. 75; 4 Watts' R. 334. Vide 
Dalloz, Dict. h.t., and Salary. See Counsellor at law.