The body of knowledge, especially of a traditional, anecdotal, or popular nature, on a particular subject
Accumulated facts, traditions, or beliefs about a particular subject.
The authentic works of a writer
A sanctioned or accepted group or body of related works
An accepted principle or rule
A criterion or standard of judgment
A body of principles, rules, standards, or norms
The game Canon would have to be added to as the time goes past the last the time of BS2. Also the content and details in the games are often vague with many things alluded to and expressed as opinions (there is no authoritive narrator) and limited to what we see at the time we play it.
Note - Burial at Sea is NOT to be considered Canon/Lore as its fantasy contamination from Infinite BS, though some of the places/names/objects represented could be reused, but generally the plotline and its events brought a boatload of conflicts.
Expanded Lore and Canon :
Proposed Government of 'New Rapture'