This is the legal term used throughout Canada to refer to any form of sexual contact without voluntary consent. Kissing, fondling, vaginal intercourse, anal intercourse, and oral sex are all examples of sexual assault if they are done without voluntary consent.
Most sexual assaults involve people who know each other.
In Canada, the law does not distinguish between acquaintance sexual assault and assault by a stranger. Consent that is obtained through pressure, coercion, force, or threats of force is not voluntary consent. Against her will is against the law - and this applies to male victims as well. These are dangerous assumptions for both parties - the victim can be severely traumatised and the offender can be prosecuted and jailed for acting on these false assumptions. Obviously it is important for both men and women to be very clear about their intentions and their limits regarding sexual behaviour.