From WordNet (r) 2.0 (August 2003) [wn]:
Saturday
n : the seventh and last day of the week; observed as the
Sabbath by Jews and some Christians [syn: Saturday,
Sabbatum, Sat]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Saturday \Sat"ur*day\ (?; 48), n. [OE. Saterday, AS. Saeterdaeg,
Saeterndaeg, Saeternesdaeg, literally, Saturn's day, fr. L.
Saturnus Saturn + AS. daeg day; cf. L. dies Saturni.]
The seventh or last day of the week; the day following Friday
and preceding Sunday.
[1913 Webster]