To admire one's abs either by:
Lifting of the top - stroking the abs to check that you are still lean; or
Lifting of the top or having no top on at all and admiring oneself in a mirror or indeed any reflection you can see.
NB. Lighting is key to these disciplines and can improve the illusion of being 'stacked' and 'ripped' ten fold.
Man or Woman is feeling a bit insecure and 'fatty lumpkins' so they seek the nearest reflection with good lighting and stroke their abs to reasure themselves of their leanness - i.e having an ab-down.
This behaviour is often seen by man who's just been blown out by a girl in a bar.
Girl in a bar "It's not you it's me, but i still want to be your friend"
Bloke rushes off to nearest mirror (mirror in the mens toilets) he then lifs his top and looks at his abs to prove his manlyness