la·bel·lum 
(lə-bĕləm)
(lə-bĕləm)n. pl. la·bel·la (-bĕlə)
1. The median petal of an orchid flower, usually different in shape, size, or color from the two lateral petals; lip.
2. A liplike part, such as the tip of the labium of certain flies, used for lapping up liquids.
[Latin, diminutive of labrum, lip; see leb- in the Appendix of Indo-European roots.]
la·bellate (-ĭt) adj.