A phrase used to express glee when an fortunate event occurs that allows the individual to get something or "come up" on something for nothing. In lamest terms, getting something for nothing.
I saw that basketball player leave his locker open. I'm gonna get some new shoes on the come up.
We're gonna see Batman cheap during the matinee and watch three other movies that day on the come up.
To work yourself into the proximity of your desired subject with the sole purpose of shamelessly hitting on them. Said subject is usually aware of your stalking and may be seen rolling her eyes and muttering, Lord, he is creeping up on the come up AGAIN!'
Ok, ladies, stick together. Keep an eye out for nerdlingers trying to creep up on the come up!
When they first met, he thought she was just creeping up on the come up but as it turned out she wasn't skeevy like that at all.