Wiktionary (0.00 / 0 votes) Rate this definition: heather (Noun). An evergreen plant, Calluna vulgaris, with spiky leaves and small purple, pink, or white flowers. heather (Noun). The Ericaceae family. heather (Noun). Various species of the genus Erica. heather (Noun). Various species of the genus Cassiope.earby & related entries: 1  heathenized. 2  heathenizing. 3  heathenness. 4  heathenry. 5  heathens. 6  heather bell. 7  heather mixture. 8  heather-bell. 9  heather-mixture. 10  heathered.