HONORARIUM
honorarium
(noun) a fee paid for a nominally free service
Source: WordNet® 3.1
Etymology
Noun
honorarium (plural honorariums or honoraria)
Compensation for services that do not have a predetermined value.
Source: Wiktionary
Hon`o*ra"ri*um, Hon"or*a*ry, n. Etym: [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.
2. (Law)
Definition: An honorary payment, usually in recognition of services for
which it is not usual or not lawful to assign a fixed business price.
Heumann.
Source: Webster’s Unabridged Dictionary 1913 Edition