Discussion Groups / English Usage / June 2010

That subject was discussed, without a firm conclusion. The term
"siphon" has already been extended, as shown here (found through
onelook.com) :

(M-W)
2 : any of various tubular organs in animals and especially mollusks
or arthropods that are used for drawing in or ejecting fluids

(AHD)
Zoology A tubular organ, especially of aquatic invertebrates such as
squids or clams, by which water is taken in or expelled.

(CALD)
soda siphon: a bottle for filling water with gas and forcing it out
under pressure to use in drinks

(ENCARTA)
2. illegally tap funds or resources: to convey or draw money or
resources from something, especially illegally

So, to me it seems reasonable to apply the extended term to physical
structures that transfer a fluid through a tube sealed against the
environment except at the ends, using some combination of the weight
of the fluid and pressure differentials between the two ends. Using
these criteria, both a soda straw and BP's capture tube could be
called siphons.

It seems less reasonable to apply the term to a peristaltic tube,
where energy is supplied other than by fluid weight or differential
pressure, but some of those might be included in the zoological uses.
(I don't know.)

The metaphoric use (illegally tap funds) seems apt, in that the
transfer is done by rearranging a flow and the mechanism has to remain
sealed (secret) for it to keep working.