What Does Hook Up Mean (Social Interaction)?

This.

It is probably becoming, however, more sexual over time, the same way that the terms “intercourse” and “making love” became inherently sexual. Read some 19th century novels where the heroine “makes love” with her boyfriend in the park in broad daylight, or where a boy walks home from school with a girl and turns around and writes a letter to his BFF about how awesome it was to have “intercourse” with a lady. It wasn’t always inherently horizontal, though of course there was an implication that it could eventually lead to activities that were more horizontal in nature.

The delightful ambiguity of the phrase is what’s cool about it. It means everything from deep kissing to the horizontal mambo.