Webster’s Revised Unabridged Dictionary · 1913
Dogwatch
Dog′watch′ (·wŏch′), n. (Naut.) A half watch; a watch of two hours, of which there are two, the first dogwatch from 4 to 6 o'clock, p. m., and the second dogwatch from 6 to 8 o'clock, p. m. Totten.