Refers to a group-hug that you give to both a person of the opposite gender whom you like very much and his/her main squeeze; the theory is that this will reduce the chance of said significant other's feeling jealous or "left out", the way he/she might feel if you merely hugged your "target" person "individually".
Initially administering a diluted embrace does not necessarily mean that you are forfeiting your option to give your opposite-gender friend a "separate" hug at some point during your period of visiting with the pair of lovers; often, this "communal arms-around" can merely be the first of at least two such warm embraces; it can just be what you do as a "hello; so nice to see you" greeting when you first bump into the couple. After you all have finished exchanging friendly small talk or whatever else the three of you choose to share during that particular meeting, you probably can then give each of the two people an "individual" hug to say goodbye, which of course will allow you to cuddle up to your "target" person "exclusively" for a moment after all; extra points if this time you make sure to embrace the person's significant other first --- i.e., before you clasp your "target" person --- so that he/she will not have to wonder if he is gonna "get some lovies", too.