Definition of pentadelphous in US English:

pentadelphous

adjective

Botany
  • (Of stamens) arranged in five groups; (of a plant) having the stamens so arranged.

Origin

Mid 19th century; earliest use found in John Lindley (1799–1865), botanist and horticulturist. From penta- + ancient Greek ἀδελϕός brother + -ous.