A four-propeller airplane can be referred to in a number of different ways, depending on the circumstances and context. One common term is "quad-engine aircraft," which emphasizes the fact that the plane has four separate engines powering its propellers. Another term that may be used is "twin-tailed aircraft," which refers to the presence of two physical tails at the rear of the plane. Other possible synonyms include "multi-engine plane," "four-engine prop plane," or simply "four-prop plane." Ultimately, the most appropriate term will depend on the specific situation and the desired level of detail and specificity.