RET-ro-COL-lis, noun, from Latin "retro" (backwards) and "collum" (neck).
A form of torticollis, or spasm of the neck muscles, that particularly affects the muscles in the back of the neck, pulling the head backwards. May be present in a number of neurological disorders, including neurodegenerative diseases like progressive supranuclear palsy and iatrogenic conditions like tardive dyskinesia.