Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sĭlentĭōsē, adv., v. silentiosus fin.
sĭlentĭōsus, a, um, adj. [silentium], perfectly still or silent: nactus opacae noctis silentiosa secreta, App. M. 11 init.
Adv.: sĭlentĭōsē, stilly, silently: silentiose geritur publicum bonum, Cassiod. Var. 11, 1 med.