Manual release is an alternative term to masturbation. It is a sexual climax that occurs as a result of manual stimulation.
More About Manual Release
Manual release is a less used, more technical term for masturbation or manual sex. The term is used in situations like so-called happy ending massages where the happy ending is a manual release. Manual release can be done mutually, as in the case of mutual masturbation where each partner is manually stimulated to climax.