Definition of wyvern in US English:

wyvern

noun

Heraldry
  • A winged two-legged dragon with a barbed tail.

    • ‘The wyvern was the emblem of the rulers of Wessex and the word "wyvern" is associated with the many areas of Wessex, reflected in many county and town heraldries of the South West and west of England.’
    • ‘A golden wyvern was featured on the flag of King Harold (Goodwinson/ Godewineson) of Wessex and is depicted in the Bayeux Tapestry.’
    • ‘Stephen Friar speculates that the wyvern entered British heraldry as the standard of the Roman cohort and later appeared as the "burning dragon" of Cadwallader (the origin of the red dragon of Wales).’

Origin

Late Middle English (denoting a viper): from Old French wivre, from Latin vipera.

Pronunciation

wyvern

/ˈwaɪvərn//ˈwīvərn/