semi-ˈannual, a. (and n.)
[semi- 6 b. Cf. L. sēmi-annuus in sense 2, and F. semi-annuel.]
1. Recurring every half-year; half-yearly.
| 1794 [see semi-diurnal 2]. 1803 Phil. Trans. XCIII. 470 Semi-annual solar Equation, Precession, and Refraction. 1860 (title) Semi-Annual United States Register. 1866 Crump Banking i. 33 Merchants are not in the habit of placing a semi-annual or even annual statement of their position before the public. 1868 Rep. U.S. Comm. Agric. (1869) 260 [Esparto] becoming more vigorous and abundant with yearly or semi-annual gathering. |
2. Lasting for half a year (only); esp. of plants. Also n. = semi-annual plant.
| 1882 Encycl. Brit. XIV. 857/1 The higher plants may be classed, according to duration of life, as follows:—annuals, or semi-annuals..biennials. 1888 Dawson Geol. Hist. Plants 258 Arctic semi-annual days and nights. |
So semi-ˈannually adv., every half-year, once in every six months.
| 1828–32 in Webster. 1889 Farmer Americanisms s.v. Papabotte, It visits the Western prairies in large numbers semi-annually; early in the spring and late in the summer. |