P-wave
Primary or compressional waves. P waves are the fastest body waves and arrive before the S waves, or secondary waves. The P waves carry energy through the Earth as longitudinal waves, moving particles in the same line as the direction of the wave. P waves can travel through all layers of the Earth.  In a slinky, compressional waves are generated if one end of a stretched slinky is pushed quickly along the axis of the slinky.

(Adapted from: Isachson, Y. W., E. Landing, and J. M. Lauber, P-wave Wave in a Slinky.)