Emily Dickinson Lexicon

SU-PINE, a. [L. supinus.]

1. Lying on the back, or with the face upward; opposed to prone.
2. Leaning backward; or inclining with exposure to the sun. If the vine / On rising ground be plac'd on hills supine. – Dryden.
3. Negligent; heedless; indolent; thoughtless; inattentive. He became pusillanimous and supine, and openly exposed to any temptation. – Woodward. These men suffer by their supine credulity. – K. Charles.