VPL
From wipipedia.org
VPL or visible panty line is the outline of the edge of someone's underwear visible across their buttocks under a skirt, dress, trousers, catsuit, etc. This may be an indentation caused by a tight or elasticated edge, or the outer garment may be slightly see-through.
Normally, only the lower edge of the underwear is visible. However, the top may also be visible, especially when there is see-through.