Full Idea
The best definition of reliabilism seems to be: the agent has evidence, and bases the belief on the evidence, and the actual conditional reliability of the belief on the evidence is high enough.
Gist of Idea
Reliabilist knowledge is evidence based belief, with high conditional probability
Source
Juan Comesaña (Reliabilism [2011], 4.4)
Book Reference
'Routledge Companion to Epistemology', ed/tr. Bernecker,S/Pritchard,D [Routledge 2014], p.185
A Reaction
This is Comesaña's own theory, derived from Alston 1998, and based on conditional probabilities.