In modern Hebrew, אימוץ or לאמץ means to *adopt*.
In Biblical Hebrew there is no word for *adopt* [to the best of my knowledge]. The word לאמץ means to strengthen, as in חזק ואמץ. There is a pasuk in Tehillim [פ' ט"ז] that says "ועל בן אמצתה לך" but it doesn't mean the son you adopted but the son you strengthened.
