The Collaborative International Dictionary of English v.0.48:
Gallows \Gal"lows\, n. sing.; pl. Gallowsesor Gallows. [OE.
galwes, pl., AS. galga, gealga, gallows, cross; akin to D.
galg gallows, OS. & OHG. galgo, G. galgen, Icel. g[=a]lgi,
Sw. & Dan. galge, Goth. galga a cross. Etymologically and
historically considered, gallows is a noun in the plural
number, but it is used as a singular, and hence is preceded
by a; as, a gallows.]
1. A frame from which is suspended the rope with which
criminals are executed by hanging, usually consisting of
two upright posts and a crossbeam on the top; also, a like
frame for suspending anything.
So they hanged Haman on the gallows. --Esther vii.
If I hang, I'll make a fat pair of gallows. --Shak.
O, there were desolation of gaolers and gallowses!
2. A wretch who deserves the gallows. [R.] --Shak.
3. (Print.) The rest for the tympan when raised.
4. pl. A pair of suspenders or braces. [Colloq.]
Gallows bird, a person who deserves the gallows. [Colloq.]
Gallows bitts (Naut.), one of two or more frames amidships
on deck for supporting spare spars; -- called also
gallows, gallows top, gallows frame, etc.
(a) The frame supporting the beam of an engine.
(b) (Naut.) Gallows bitts.
Gallows tree, or
Gallow tree, the gallows.
At length him nail['e]d on a gallow tree. --Spenser.