This question either comes up explicitly in discussions of privacy and identity, or lurks unspoken beneath the surface. We talk a lot about online trust, and only occasionally does someone stop and ask if we’ve defined just what it is that we’re talking about.
Some people reply, at that point, that trying to define trust is a rat-hole/red herring/exercise in yak-shaving, but I am less pessimistic. Here’s a simple definition of trust which I think is flexible enough to serve as a basis for productive discussion, while still covering the essentials. Of course, if you disagree, I’d welcome comments!
“Trust is the belief that someone else will act in your interests, even if they have the opportunity and the motivation to do otherwise.”
It’s a belief, and like any belief, it may be well- or ill-founded. You may be mistaken or misinformed, or the other party may be deceiving you.
As I say, it’s not necessarily a perfect definition, but it has worked for me so far.