to mistake (for something or someone else); to be unable to recognize
彼女はすっかり見違えた。
She had changed completely, I barely recognized her.
庭師のおかげで、庭が見違えて綺麗になった。
Thanks to the gardener, the garden was transformed and became beautiful.
徹底的な改装で、建物は見違えるほど変わるだろう。
With a thorough renovation, the building will change so much it will be unrecognizable.