A humerous phrase indicating a simultanious happening.
Derived from old Western TV shows or movies. Something exciting would be happening out on the range somewhere (or in town, etc), but at the same time something else would be happening at the home base, i.e. the ranch.
The bank is being robbed by Smoky Joe and the Goatnose Gang! Will Whitehat Willy be able to foil the desperadoes in time?
Meanwhile, back at the ranch, little Betsy has discovered a gold nugget in the family's stream.
To have sex with your chick then walk away about 2 minutes in. Three hours later tackle her to the ground and carry on with the sexy times.
Mary: Where did you get them bruises from Sandra?
Sandra: Shaun gave me the quarter back sneak last night,
the little bastard.
Mary: The fucker! Adam did that the other day to me, got me whilst I was ironing and burnt me ricker on the iron!
When after cumming into a someones mouth you ask them to "pass it back", the sperm is then transferred from the original recipient's mouth to it's original owners mouth by any means. After this takes place the sperm is then swallowed by it's maker.
Your girlfriend is giving you head, and you cum into her mouth; however, you ask her not to swallow, but to instead, pass it back, put your own sperm into your moth so you can swallow it.