When a girl pins down another girl or a guy in a wrestling match (usually if it's a guy the match was staged, unless the dude is just a big panzy, and/or lets her win for the enjoyment of having this move done on him) by laying on top of them, them being face up and she being face down, and then presses her boobs (they're usually big or else this is pointless) down over their face, smothering them with her massive rack. When a girl does this to a guy, the guy is in a state of extreme bliss, and when a girl does this to another girl, then all guys watching are in a state of extreme bliss, but wish they were underneath as well.
If a guy does this to a girl, well then he's mean for laying his fat self (he's gotta be fat to have boobs) on a poor girl, and if a guy does this to a guy, you will effectively be boner-killed for the rest of your life. Avoid at all costs if you ever want to masturbate again.
A girl lays down on another girl and uses her boobs to smother her face, thus, a breast smother. *fap fap fap fap*