If the medium oscillates perpendicular to the direction of propagation, the wave is:

1. Waves are classified by how the medium moves relative to the wave. 2. One class has the medium moving across the direction of travel. 3. If the constituents oscillate perpendicular to the direction of propagation, the wave is transverse. 4. So the answer is transverse. _Source: syllabus Physics Part II, Ch 14 'Waves'_