Rate of fire, often abbreviated ROF, refers to how quickly a weapon can fire, rearm/reload and fire again. Each weapon has its own rate of fire. This is one of the variables used to calculate the total damage per second that a unit can inflict.
The rate of fire has two components. The first is the amount of times the weapon can fire per second. A value less than one means that there is a pause of more than one second between shots. The second component is the number of projectiles that are launched each time the weapon fires.
Rate of fire: 1.5 × 4
This indicates that the weapon fires 4 missiles, pauses for 0.66 seconds, and then fires 4 more missiles.