pa·pil·i·o·na·ceous 
(pə-pĭl′ē-ə-nāshəs)
(pə-pĭl′ē-ə-nāshəs)adj.
Having a bilaterally symmetrical corolla somewhat resembling a butterfly, characteristic of certain plants of the pea family such as a sweet pea.
[Latin pāpiliō, pāpiliōn-, butterfly; see PAVILION + -ACEOUS.]