One who enjoys feeling women's breasts, but is far too rough with them causing the women a great deal of pain. This can also be to describe someone who doesn't know how to approach or handle a delicate situation, or it can be used just as a general insult.
Example 1: (Breast Toucher)
My breasts are killing me!
My boyfriend is such a tittymasher!
Example 2: (General Frustration Insult)
Dude...IHACK3457 will not stop camping me!
Yea, I know that guy..fuckin tittymasher
Example 3: (Delicate Situation)
Dick: Hey guys, we have been friends along time right?
Tom: Sure, why whats up?
Dick: Well you should probably know then..Im gay.
Harry: OH MY GAWD WHAT THE THE HELL!?!?! ARE YOU KIDDING ME?!