Definition from Wiktionary, the free dictionary
gumline (plural gumlines)
- The line along the top of the gums, where they meet the surface of the teeth
2007 December 20, Martha Schindler Connors, “Pearly Wisdom”, in New York Times:
- BEWARE OF BLOOD Leaving plaque along the gumline leaves gums swollen and inflamed and apt to bleed.