sēmĭ-hōra, ae, f.,
a half-hour , half an hour , Cic. Rab. Perd. 2, 6; Cels. 3, 21; Petr. 69, 4; Auct. B. Afr. 38.
sēmi-hōra ae, f a half-hour, half an hour. ...
An Elementary Latin Dictionary