[hook up]/[hooked up]
To engage in romantic/sexual activity with another at a party/gathering.
Usually, one or both partners are under the influence of alcohol, or another judgement imparing drug. Hooking up usually involves little or no emotional attachment.
An exchange. To give/recieve/share an asset, or something of value, usually something that is tangible.
Hooking up is most commonly used in reference to the sale/exchange of illict drugs.