A sealed metal vessel in which the ingredients of a drink are shaken hard with ice to chill, dilute and aerate them in a few seconds before straining into the glass. The two common designs are the cobbler, a three-piece shaker with a built-in strainer cap, and the Boston or tin-on-tin, two cups sealed together and used with a separate strainer. Drinks containing juice, dairy, egg white or syrup are shaken; drinks made only of spirits are usually stirred in a mixing glass instead, since shaking clouds them.
A dozen hard shakes over ten to fifteen seconds is enough. The shaker frosts on the outside when the drink is cold. A jar with a tight lid stands in for one at home.
Preparation terms include fat washing for flavor infusion and oleo saccharum for citrus-peel syrup.