Overnight is a subtle way to refer to having casual sex. It hints at spending the night at a person's home, presumably to get to know them better sexually. Of course, one does not need to spend the whole night at a partner's place. They don't even need to do the deed during night time, at all. The term 'overnight' is just a safe way to talk about it. It's like "Netflix and chill” without unnecessarily getting a TV/movie addict partner excited for the wrong reasons.
More About Overnight (OVN)
There is only one item necessary when packing for an 'overnight.' That is: protection. When sex is casual and commitment isn't a requisite, then it is best to use contraceptives and barriers. Latex condoms are best for males. Other than this, one can come as they are. After all, the best sex is with people who are comfortable with themselves, emotionally and sexually.
