fiduciary
Concise Oxford English Dictionary © 2008 Oxford University Press:
fiduciary /fɪˈdjuːʃ(ə)ri/
▶adjective
- 1 Law involving trust, especially with regard to the relationship between a trustee and a beneficiary.
- 2 Finance (of a paper currency) depending for its value on securities or the reputation of the issuer.
– origin C16 (in the sense ‘credentials’): from L. fiduciarius, from fiducia ‘trust’.
'fiduciary' also found in these Oxford entries:

