In Old Norse, it's the neuter accusative singular past participle used to form the perfect tense.

http://www.utexas.edu/cola/centers/lrc/eieol/norol-3-X.html#Nor03_GP14_02

(Google tip: "supine" + "old norse"!)

--- In norse_course@yahoogroups.com, CalecM@... wrote:
>
> Faulkes in NION uses the term "supine." Now, I'm a bit egotistical about
> my vocabulary, but this one stumped me, so I had to hit the web. It seems
> to be very synonymous with "gerund," but as Faulkes uses it, it doesn't
> seem to be. And the web definitions seem to refer primarily to Latin. Would
> someone be kind enough to help me with the meaning of this term as it
> applies to ON?
>
> Thx,
> Alec
>