Definition of priors:
(adj) :
Coming before in order or time; earlier, former, previous.
(adj) :
More important or significant.
(adv) :
Chiefly followed by to: in advance, before, previously.
(adj) :
(Bayesian statistics) Chiefly in prior probability: of the probability of an event: determined without knowledge of the occurrence of other events that bear on it, before additional data is collected.
(n) :
(Bayesian statistics) A prior probability distribution, that is, one determined without knowledge of the occurrence of other events that bear on it, before additional data is collected.
(n) :
(by extension) In the rationalsphere: a belief supported by previous evidence or experience that one can use to make inferences about the future.