A mother who is intensely hot, causing an immediate physical reaction and desire to be with her or race home and, um, remember her. Said mom is so attractive that, if she was in a photo with all of her children, a man would be compelled to crop the image to focus on just her, which would be especially useful in his private time.
Wow, look at that mom over there with all those kids. Don't know how she does it, but damn... she's croppable!
A part of the group photo that can be cropped to make a separate picture.
Look! Jack and Jill totally look croppable!