Defn: Half or imperfectly transparent; translucent. Woodward.

SEMIDIATESSARON
Sem`i*di`a*tes"sa*ron, n. (Mus.)

Defn: An imperfect or diminished fourth. [R.]

SEMI-DIESEL
Sem`i-Die"sel, a.

Defn: Designating an internal-combustion engine of a type resembling the Diesel engine in using as fuel heavy oil which is injected in a spray just before the end of the compression stroke and is fired without electrical ignition. The fuel is sprayed into an iron box (called a hot bulb or hot pot) opening into the combustion chamber, and heated for ignition by a blast-lamp until the engine is running, when it is, ordinarily, kept red hot by the heat of combustion.

SEMIDITONE
Sem`i*di"tone`, n. Etym: [Pref. semi- + ditone: cf. It. semiditono.
Cf. Hemiditone.] (Gr. Mus.)

Defn: A lesser third, having its terms as 6 to 5; a hemiditone. [R.]

SEMIDIURNAL
Sem`i*di*ur"nal, a.

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

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