echinus

noun
  1. 1

    A sea urchin.

  2. 2

    The rounded moulding forming the bell of the capital of the Grecian Doric style, which is of a peculiar elastic curve.

  3. 3

    The quarter-round moulding (ovolo) of the Roman Doric style.

  4. 4

    The egg-and-anchor or egg-and-dart moulding, because often identified with the Roman Doric capital.

Source: https://en.wiktionary.org/wiki/echinus