To attach or join securely in place. Please fasten your seatbelt before the plane takes off.
He fastened the lid tightly to prevent any leaks.
To close or lock something. She fastened the door before leaving the house.
To become attached or joined. The two pieces of metal fastened together as the glue dried.
To focus or direct one’s gaze, mind, or attention intently on something, usually followed by "on" or "upon". Her eyes fastened on the mysterious figure in the doorway.