We don't have synonyms for triquetra yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are triquetral, triquetrum and triquetric.
(n) :
A shape formed of three vesicae piscium, sometimes with an additional circle, a symbol of things and persons that are threefold (including the Christian Trinity), and a symbol of protection in Wicca.
(n) :
A shape formed of three vesicae piscium, sometimes with an additional circle, a symbol of things and persons that are threefold (including the Christian Trinity), and a symbol of protection in Wicca.