Adverb
In an immovable manner.
Source: Webster's dictionarythe mountains brooded immovably above the river Source: Internet
Thou didst adorn the divine see of Peter, and since from this divine Rock, thou didst immovably defend the Church, so now thou art glorified with him.” Source: Internet
For many months in half darkness, Theseus sat immovably fixed to the rock, mourning for both his friend and for himself. Source: Internet