Fronting

The fancy name for this body clue is ventral fronting, which refers to moving the front half of the torso forward. Ventral fronting is a good clue that someone feels comfortable around you for two reasons: 1) unless you're Kate Moss, your torso makes up a significant part of your body mass and moving it dishonestly takes a lot of energy and 2) the ventral side of your torso contains the chest, the organs, the heart, and the genitals. It implies that your partner trusts you will not damage any of these vital parts.