semidiurnal

Of, relating to, occurring, or performed during half a day.

Occurring or coming approximately once every 12 hours, as the tides.

Of or relating to the arc described by a celestial body between its meridian passage and its points of rising or setting.

Pertaining to or accomplished in half a day (either twelve hours or six hours); continuing half a day.

In entomology, partly diurnal; flying in twilight; crepuscular; specifically, of or pertaining to the Semidiurna.

Pertaining to, or accomplished in, half a day, or twelve hours; occurring twice every day.

Pertaining to, or traversed in, six hours, or in half the time between the rising and setting of a heavenly body.

Twice daily (usually of tides).