an informal agreement for people to get together at a subsequent time

Hooking up refers to having sex, messing around refers to anything else (mostly beneath the waist) and making out is just making out. Done. Hooking up is having sex with no expectations or strings attached.

for middle school: making out.
for high school and beyond: any type of sexual activities usually refering to sex.

v. To provide or return.

Depends where you are from, its different for different states, even different cities. In Vermont it means having sex, in Mass. it means anything but sex and in Maine it either means hanging out or a one night stand deal depending on what area your from.

Sex for its own sake; when one or both of its participants doesn't want or doesn't know if they want a committed relationship but are horny. Usually, sex early on, especially on the first date, is the hallmark sign of a hook-up.

To be given somthing for free or at a discount usuly by a Homie.

Background from , hook me up to the obvious been hooked-up