noun

• A hypocycloid with four cusps (like a square with concave sides).

  ‘The astroid was first discussed by Johann Bernoulli in 1691-92.’

  More example sentences

  • ‘The caustic of the tricuspoid, where the rays are parallel and in any direction, is an astroid.’
  • ‘The cycloidal curves, including the astroid, were discovered by Roemer (1674) in his search for the best form for gear teeth.’
  • ‘An astroid is a specialized case of the general hypocycloid family of curves.’
  • ‘The astroid is a famous curve that arises in an interesting way.’