"Meet up" vs. "meet" vs. "hook up"

What's the difference between meet up, meet and hook up as a synonym of meet up?

The Free Dictionary has the following definitions:

• to meet up: to see and talk to someone familiar or someone you do not know: "Let's meet up for drinks after work."
• to hook up: to meet someone and spend time together: "I was traveling alone, but then I hooked up with another woman about my age."

These definitions are really similar. What is the subtle difference between these three words?

Solution 1:

Hook up in common American parlance (among the under forty set) means to engage in sexual acts.

Meet (in this context) and meet up mean meet, that is, connect at a time and place.