For the very-far-from-last word on the subject, try

http://www.straightdope.com/classics/a961108a.html

And here's a very different definition, from Bartleby:

E. Cobham Brewer 1810–1897. Dictionary of Phrase and Fable. 1898.

Runcible Spoon (A)...A horn spoon with a bowl at each end, one the size of a table-spoon and the other the size of a tea-spoon. There is a joint midway between the two bowls by which the bowls can be folded over


...There may be more to this runcibility business than meets the eye !