pa·pil·i·o·na·ceous \ ̷ ̷| ̷ ̷ ̷ ̷ ̷ ̷|nāshəs\adjective Etymology: Latin papilion-, papilio + English -aceous 1.: resembling a butterfly; specifically: irregular and suggestive of a butterfly in shape < the corolla of many leguminous plants is papilionaceous > 2.[New Latin Papilionaceae + English -ous]: of or relating to the family Leguminosae