The Collaborative International Dictionary of English v.0.48:

Questor \Ques"tor\, n. [L. quaestor, contr. fr. quaesitor, fr.
   quaerere, quaesitum, to seek for, ask: cf. F. questeur.]
   (Rom. Antiq.)
   An officer who had the management of the public treasure; a
   receiver of taxes, tribute, etc.; treasurer of state.
   [Written also qu[ae]stor.]
   [1913 Webster]

   Note: At an early period there were also public accusers
         styled questors, but the office was soon abolished.
         [1913 Webster]

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

QUESTOR or QUAESTOR, civil law. A name which was given to two distinct
classes of Roman officers. One of which was called quaestores classici, and
the other quaestores parricidii,
     2. The quaestores classici were officers entrusted with the care of the
public money. Their duties consisted in making the necessary payments from
the aerarium, and receiving the public revenues. Of both, they had to keep
correct accounts in their tabulae publicae. Demands which any one might have
on the aerarium, and outstanding debts were likewise registered by them.
Fines to be paid to the public treasury were registered and exacted by them.
They were likewise to provide proper accommodations for foreign ambassadors
and such persons as were connected with the republic by ties of public
hospitality. Lastly, they were charged with the care of the burials and
monuments of distinguished men, the expenses for which had been decreed by
the senate to be paid, by the treasury. Their number at first was confined
to two, but this was afterwards increased as the empire became, extended.
There were questors of cities, provinces, and questors of the army, the
latter were in fact pay-masters.
     3. The questores parricidii were public accusers, two in number, who
conducted the accusation of persons guilty of murder or any other capital
offence, and carried the sentence into execution. They ceased to be
appointed at an early period, Smith's Dic. Gr. and Rom. Antiq. h.v.