In response to DaveMatrix's comment that fantasizing about another person always lust....
1. If the person you are fantasizing about is your spouse, and what you are thinking of is something they would condone, but for some reason you can't be with them, it is debatable if this is lust.
2. Phone sex with you spouse, similar to above.
3. If one considers eating and drinking, eating is not gluttony and having a glass of wine is not drunkenness. That is, a legitimate use is not cancelled by an abuse. It may follow that masturbation is not necessarily sinful, e.g. if lust is not present, or if one imagines having loving sexual relations with one’s spouse.
4. In light of those possibilities, without condoning nor condemning masturbation, Dr. Doug Weiss, in his book “Sex, Men and God: A Godly Man’s Roadmap to Sexual Success”, describes two mental postures possible in masturbation. In the first mental posture, others are objectified and used for base gratification. This is clearly sinful and leads to unhealthy patterns of behavior. So much of our culture emphasizes this posture that it is hard for us to imagine any other. Indeed, some suggest it is not possible to avoid inappropriate thoughts, implying masturbation cannot be without sin.
In contrast to this, in the second mental posture suggested by Dr. Weiss, improper thoughts involving others are not entertained, and the experience, while sensual, is truly solitary. Dr. Weiss suggests that masturbation from this second posture does not carry the problems inherent in the first. That is, in itself, the sexual pleasure associated with self-stimulation is not necessarily sinful, so long as inappropriate thoughts are not indulged.
As the Y, its my favorite restaurant