Fetching details from the dictionary...
firm; solid; steady; secure; unshakeable; unwavering
彼女の信念は揺るぎなかった。
Her conviction was unshakeable.
彼は不況下でも会社を揺るぎなく信じた。
He unwaveringly believed in his company even during the recession.
引退後も彼の揺るぎない評判は健在だ。
Even after retirement, his unshakeable reputation remains intact.