Adverb (fukushi), Suru verb
silent (as the grave); deadly silent; deathly quiet
Onomatopoeic or mimetic word
シンと静まった部室。響くのは、クロッキー帳に擦れる鉛筆の音だけ。The club room returned to quiet. All that could be heard was the sound of pencil on sketchpad.
Also written シンと