That's not a good definition of 'friend' but if you insist on it, I'd qualify. I have a handful of people I consider friends by my definition, but nobody I'd truly confide in at a non-trivial depth about my personal life. I think there are a lot of people like me, who basically keep everybody at arm's length and trust nobody with the sorts of deep confidences that more open people like to share. Mainly because they don't feel the need, not because they are untrusting types.

Friendship being reciprocal, I don't think anyone I know sees me as a deep, intimate friend. I am a good, long-time friend to a few people, but nobody's best buddy or closest confidant. I don't want to be, and I don't want one. Haven't had one since fourth grade. I avoid accepting confidences as much as I avoid sharing my own. I try to be of practical use to friends in need, and look for practical help myself when necessary, but that's it. Some people don't accept such a priori depth-limited relationships. It's eventually-all or nothing for them. As you might expect, I have no friends of this type.

That leads to the occasional sudden sharp stab of extreme loneliness, but it tends to be momentary and far less painful than sharing deep confidences. As you age, you get used to it.

Intimacy is over-rated. Reserve is a forgotten virtue in this confessional culture of ours. The value of meeting your deeper existential challenges alone is insufficiently recognized.