The active avoidance of critical thinking, reason, or logic regarding something that is unreal or impossible in reality.
Unlike the porous self where man and cosmos are one—where, in their worldview, the impossible is possible—the willing suspension of disbelief affects someone who knows that what they're witnessing or experiencing is impossible, and yet they choose to believe anyways.
Source: Used by Charles Taylor in Biographia Literaria (not yet planted) to describe reader's brief belief of speculative fiction in order to enjoy the narrative.