From The Collaborative International Dictionary of English v.0.48 [gcide]:
Stanchion \Stan"chion\ (st[a^]n"sh[u^]n; 277), n. [OF. estanson,
estan[,c]on, F. ['e]tan[,c]on, from OF. estance a stay, a
prop, from L. stans, stantis, standing, p. pr. of stare to
stand. See Stand, and cf. Stanza.] [Written also
stanchel.]
1. (Arch.) A prop or support; a piece of timber in the form
of a stake or post, used for a support or stay.
[1913 Webster]
2. (Naut.) Any upright post or beam used as a support, as for
the deck, the quarter rails, awnings, etc.
[1913 Webster]
3. A vertical bar for confining cattle in a stall.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
stanchion
n 1: any vertical post or rod used as a support