1. (Science: botany) Of or pertaining to a natural order of plants (Rosaceae) of which the rose is the type. It includes also the plums and cherries, meadowsweet, brambles, the strawberry, the hawthorn, applies, pears, service tress, and quinces. Like a rose in shape or appearance; as, a rosaceous corolla.
2. Of a pure purpish pink colour.
Origin: L. Rosaceus, fr. Rosa rose.