What does supine mean?

You are correct!

From our dictionary:

su•pine

Pronunciation: (
adj.sOO-pIn';
n.sOO'pIn),
[key]
adj.
1. lying on the back, face or front upward.
2. inactive, passive, or inert, esp. from indolence or indifference.
3. (of the hand) having the palm upward.

n.
1. (in Latin) a noun form derived from verbs, appearing only in the accusative and the dative-ablative, as dictU in mirAbile dictU, “wonderful to say.”
2. (in English) the simple infinitive of a verb preceded by to.
3. an analogous form in some other language.