a. Obs. rare. [f. TRI- 3 + ANNUAL.] Occurring every three years; lasting for three years; = TRIENNIAL.
1640. Par. Acc. St. Barth. by Exchange, in Archæologia, XLV. 78. Pd. the ringers for joy of the tryannual Parliament, 0. 2. 6.
1656. Earl Monm., trans. Boccalini’s Advts. fr. Parnass., I. lxix. 133. He was deputed a Triannual President of the Isle of Negrapont.
† b. Occurring thrice a year.
1901. Daily Chron., 8 June, 5/2. The ladies … we learn … will hold ‘tri-annual invitation meetings.’… That, we suppose, means an invitation once in four months.
