frozen(p), rooted(p), stock-still (adverb)

absolutely still

"frozen with horror"; "they stood rooted in astonishment"

still, stock-still (adverb)

without moving or making a sound

"he sat still as a statue"; "time stood still"; "they waited stock-still outside the door"; "he couldn't hold still any longer"

stock-still (Adjective)

Absolutely motionless, perfectly still.