attaches one thing firmly to another or closes something securely.
Emma fastens her seatbelt every time she gets in the car.
The carpenter fastens the shelf to the wall using nails.
✦ From Middle English fasten, fastnen, from Old English fæstnian (“to fasten, make fast”), from Proto-Germanic *fastinōną; equivalent to fast + -en.
to attach or join one thing to another, or to make something stay in position, using something like a belt, string, or lock
Please fasten your seatbelt before takeoff.
He used a clip to fasten the papers together.
✦ From Middle English fastnen, from Old English fæstnian (“to make fast; establish, settle, confirm”), from Proto-West Germanic *fastinōn, from Proto-Germanic *fastinōną (“to make firm, make fast”), from *fastuz (“firm, fast”).
