Is a 3 phase motor a Synchronous motor?

A synchronous motor can be a type of 3-Phase AC motor, or not.

A synchronous motor is defined by the period of the rotor being synchronized with the frequency of the stator windings' current. The stator windings might be 3-Phase or not (2-Phase would work).

Also synchronous motors are not the only type of 3-Phase AC motors. An induction motor could also be 3-Phase AC and has a few advantages and disadvantages over a synchronous motor.