(lip) 1. The lower of the three petals of an orchid flower, which differs in morphology and patterning from the two lateral petals and gives the flower its characteristic form. The laterals and the sepals may all be similar but the labellum is always distinct and usually much larger than the other perianth segments. It serves as a platform for pollinating insects, which are attracted by its distinctive colours and markings. See also pseudocopulation
2. The platform formed by the lower petal or group of fused petals in various other lipped flowers, such as those of the Labiatae, Scrophulariaceae, and Leguminosae.