We don't have synonyms for binormal yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are abnormal, normal and informal.
(n) :
(mathematics) A line that is at right angles to both the normal and the tangent of a point on a curve and, together with them, forms three orthogonal axes
(n) :
(mathematics) A line that is at right angles to both the normal and the tangent of a point on a curve and, together with them, forms three orthogonal axes