1. A tool that has a heavy metal head attached to a handle and which is used for hitting nails or pounding and breaking things apart: The carpenter used his hammer to secure the wooden panels on the walls.
2. The part of a gun-lock that hits the primer or firing pin and causes a gun to shoot: When he pulled the trigger of the revolver, the hammer caused the bullet to fire and to leave through the barrel.
3. One of the padded wooden pieces of a piano that strikes a long piece of wire that is fixed across a musical instrument, like a harpsichord, when the player presses a key: When a musician depresses the black or white pieces of wood at the front of the piano, each hammer hits a tuned string that produces music.

1. To force something into a particular place or shape by hitting it with a hand tool: Jason will hammer the dent out of the fender of the car today.
2. To use a striker that is covered in felt and that causes the piano strings to vibrate: Mary's mother commented, "Mary, if you hammer the cembalo keys, you might actually be hammering some good tunes!"
3. To hit something in a very forceful way: The people in this area can be sure that the next hurricane will hammer many more towns.
4. To keep talking about something or trying to get something done: Julia apparently is hammering her political opponent for his failure to cut taxes.

To talk on and on in an annoying way: Every time Mildred gets on the phone, all she can do is yammer and yammer about how her husband disappoints her.

No matter where Sally goes, it's amazing how many people she sees who are yammering on their cell phones.