TDLR: I'd like to revive the topic of the adonis_belt tag. It's currently aliased to groin. I believe it should either be aliased to hip_bones or else revived and given a clearer definition. Gross anatomy sure as hell is not my strong suit, so I apologize in advance for the lengthy explanation.
Links to previous forum topics relating to this tag:
Examples (all are rating:safe):
- adonis belt (tagged as groin but the groin isn't actually visible): post #4459689
- adonis belt and groin: post #4419428, post #4415179 (If you look at the left side, the artist left a small gap between the two)
- abs and groin but no adonis belt: post #4312744, 4254557
- post #4075180 is a good example of what is and isn't groin - male on the right has visible groin but the one on the left doesn't
- adonis belt (tagged as groin but the groin isn't actually visible): post #4743053, post #4389990
- adonis belt and groin: post #4486304, post #5139855
- abs and groin but no adonis belt: post #4854250, post #5217408
The original wiki for adonis_belt was pretty vague when compared to other anatomical tags with wikis. It doesn't exactly help that hip_bones isn't clear on the underlying anatomy of these bony protrusions. If you look at a person with very little muscle and body fat, the top of the pelvic bone is visible below the waist and the hip joints at the bottom can be seen just above the pubic area. The adonis belt is shaped by the ends of the abdominal and oblique muscles where they attach to the pelvic bone and it does extend from the iliac crest to the pubic bone (as per the original wiki definition). Developing these muscles, specifically the obliques, is what creates the v shape in the lower abdomen (above the hip joints.
On the other hand, the groin is the region starting at the hip joints and ending in the upper inner-thigh area. This includes the mons pubis/pubic mound (aka mound_of_venus), which is just the pad of fat that covers the pubic bone. Just like everybody has nipples, everybody has this layer of padding.
Based on all the medical and weightlifting/strength training I've looked at, the visible adonis_belt is the defined furrow in the region between the navel and groin that forms with lower abs AND well-developed lower obliques. It's because of where the obliques connect to the pubic bone that the v of the adonis belt lines up with the v of the groin. So @Evasion was correct in saying that the adonis_belt and mound_of_venus are separate things in forum #171366. A good distinction is that a person won't get arrested for public indecency by exposing their adonis belt to strangers.
Note regarding female musculature: The wider pelvis can make it look like a female with very little body fat has an adonis belt when it's just the contour of the pelvic bone. Hence the importance of developed obliques. (See post #2776751) If it's an adonis belt, there are furrows both at the top and bottom of the lower obliques. Otherwise it's just the contour along the pelvic bone to the hip joints.