a. [f. TRI- 3 + DIURNAL.] a. Comprising three days. b. Occurring three times a day.
a. 1828. J. Sterling, Ess., etc. (1848), II. 45. Various minor periods,… monthly, weekly, tridiurnal, and daily.
b. 1884. Athenæum, 10 May, 602/1. He … commenced to make tridiurnal meteorological observations and to issue a daily weather report.
