When you tie up a guy and jack him off repeatedly without stopping. After he cums a couple times, he'll become overly sensitive, and continuing to jack him is pretty intense overstimulation, so the body's natural reaction is to move away. That's why it's important to tie him down first.

Usually found in bdsm encounters.

"forced" distinguishes it from other things that are also called milking.

A casual invitation / threat used by an individual that is not afraid of fucking someone up.

When a guy (or girl) is tied up, a naked woman walks up to him, and she puts her nipples inside his mouth, forcing him to milk her and swallow her milk. Works better with large breasts.