If an individual gives you attention that is sexually charged in nature, whether it be verbal flattery or full-on touching and kissing, giving consent means that you reciprocate the feelings and, to a degree, welcome the attention.
When you tell someone “no,” you are not giving consent, and you have every right to protect your body from the unwanted attention of someone else.
If you are unable to give consent because you are under the influence of drugs or alcohol, you still have the right to protect your body, and the concept of consent still applies. Anyone who abuses you sexually when you are under the influence can be held criminally liable for the abuse. This is especially the case if your abuser deliberately intoxicates you for the purpose of initiating a sexual assault.