  Seismology was developed on Earth and shaped our model of the Earth's
interior over the 20th century. With the exception of the Philae lander, all in
situ extraterrestrial seismological effort to date was limited to other
terrestrial planets. All have in common a rigid crust above a solid mantle. The
coming years may see the installation of seismometers on Europa, Titan and
Enceladus, so it is necessary to adapt seismological concepts to the setting of
worlds with global oceans covered in ice. Here we use waveform analyses to
identify and classify wave types, developing a lexicon for icy ocean world
seismology intended to be useful to both seismologists and planetary
scientists. We use results from spectral-element simulations of broadband
seismic wavefields to adapt seismological concepts to icy ocean worlds. We
present a concise naming scheme for seismic waves and an overview of the
features of the seismic wavefield on Europa, Titan, Ganymede and Enceladus. In
close connection with geophysical interior models, we analyze simulated seismic
measurements of Europa and Titan that might be used to constrain geochemical
parameters governing the habitability of a sub-ice ocean.
