from
The Collaborative International Dictionary of English v.0.48
Transom \Tran"som\, n. [Probably fr. L. transtrum a crossbeam,
transom, from trans across. Cf. {Trestle}.]
1. (Arch.) A horizontal crossbar in a window, over a door, or
between a door and a window above it. Transom is the
horizontal, as mullion is the vertical, bar across an
opening. See Illust. of {Mullion}.
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2. (Naut.) One of the principal transverse timbers of the
stern, bolted to the sternpost and giving shape to the
stern structure; -- called also {transsummer}.
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3. (Gun.) The piece of wood or iron connecting the cheeks of
some gun carriages.
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4. (Surg.) The vane of a cross-staff. --Chambers.
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5. (Railroad) One of the crossbeams connecting the side
frames of a truck with each other.
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{Transom knees} (Shipbuilding), knees bolted to the transoms
and after timbers.
{Transom window}. (Arch.)
(a) A window divided horizontally by a transom or
transoms.
(b) A window over a door, with a transom between.
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