Webster’s Revised Unabridged Dictionary · 1913
Triquadrantal
Tri′quad·ran′tal (trī′kwŏd·răn′tal), a. [Pref. tri- + quadrantal.] (Spherical Trig.) Having three quadrants; thus, a triquadrantal triangle is one whose three sides are quadrants, and whose three angles are consequently right angles.