gyron
Concise Oxford English Dictionary © 2008 Oxford University Press:
gyron /ˈdʒʌɪr(ə)n/
▶noun Heraldry a triangular ordinary formed by two lines from the edge of the shield meeting at the fess point at 45 degrees.
– origin C16: from OFr. giron ‘gusset’.
'gyron' also found in these Oxford entries:

