semidiurnal

adjective

semi·​di·​ur·​nal ˌse-mē-dī-ˈər-nᵊl 

ˌse-ˌmī-,

-mi-

1

: relating to or accomplished in half a day

2

: occurring twice a day

3

: occurring approximately every half day

the semidiurnal tides

Word History

First Known Use

1594, in the meaning defined at sense 1