Definition of undecagon in English:

undecagon

noun

  • another term for hendecagon
    • ‘These various polygon shapes consist of, but are not limited to, triangles, squares, pentagons, hexagons, heptagons, octagons, nonagons, decagons, undecagons, and dodecagons.’
    • ‘How many diagonals are needed to divide a heptagon, a nonagon, and an undecagon into triangles?’

Origin

Early 18th century: formed irregularly from Latin undecim ‘eleven’, on the pattern of decagon.

Pronunciation

undecagon

/ʌnˈdɛkəɡ(ə)n/