longitudinal wave
noun [ C ] physics specialized uk/lɒn.dʒɪˌtjuː.dɪ.nəl ˈweɪv/ us/lɑːn.dʒəˌtuː.dɪ.nəl ˈweɪv/
纵波（物理学中振动方向与传播方向在同一方向上的波）
a wave moving in the same direction of travel as the vibrations (= fast movements backwards and forwards) of the particles of the substance through which it is travelling
Compare: transverse wave