To do something securely means to do it in a way that's safe, stable, and protected from danger or failure. When you fasten your seatbelt securely, you pull it tight and hear it click so it will hold you safely if the car stops suddenly. When you tie a boat securely to a dock, you use strong knots that won't come loose, even if waves rock the boat.

The word emphasizes doing something with enough care and strength that it won't fail when tested. A climber who ties a rope securely can trust it to hold their weight. A homeowner who locks their door securely makes it difficult for intruders to break in. Data stored securely on a computer is protected by passwords and encryption so hackers can't access it.

When something is fastened, stored, or protected securely, you don't have to worry about it failing. You can walk away from a securely locked bicycle knowing it will still be there when you return.