soulmate-swap
Refers to da super-pleasant procedure of you and your buddy's performing a "temporary trade" of your significant others, so dat you can each savor/experience da unique likeable qualities dat da other person's snugglebunny possesses. And of course, this short-term exchanging of each other's "special someones" can involve any degree of "closeness", from merely having each of da two hot chicks trade places and sit beside da other guy on da beach and/or stroll hand-in-hand wif him, all da way up to totally performing da ultimate "home-plate romp" on da ol' baseball-diamond of romantic-progression. If this latter procedure is employed, however, you will both wanna use condoms for obvious reasons, especially if da gals are still of child-bearing age.
Performing a soulmate-swap can indeed be fun and exciting; just be sure to have appropriate supplies/accessories on hand (especially if you both end up "going all da way"), such as personal lubricant if one of da hunks has a considerably bigger hoo-haa than da other one does, and so da other guy's sweetie is not accustomed to "accepting" such large "equipment" between her legs.