Ristretto
A particularly short, concentrated espresso made with less water.
A ristretto (Italian for "restricted") is an espresso made with the same amount of coffee but less water. The drink is smaller and more concentrated, and the shot is stopped earlier than a regular espresso.
In taste a ristretto is usually more intense and sweeter with less bitterness, because fewer of the compounds that dissolve later reach the cup. Exact amounts differ from café to café.