Adjective has 1 sense

• stock-still(s = adj.all) frozen, rooted - absolutely still; "frozen with horror"; "they stood rooted in astonishment"

Adverbial has 1 sense

• stock-still(r = adv.all) still - without moving or making a sound; "he couldn't hold still any longer"; "he sat still as a statue"; "they waited stock-still outside the door"; "time stood still"