dead-nettle Syllabification: (dead-net·tle)Definition of dead-nettle noun an Old World plant of the mint family, with leaves that resemble those of a nettle but lack stinging hairs. Lamium and related genera, family Labiatae: several species, including the common white dead-nettle (L. album) dead-nettle in other Oxford dictionaries Definition of dead-nettle in the British & World English dictionary