Gy*roid"al (j&isl;*roid"al), a.
[Gr. gy^ros circle + -oid + -al.]
1. Spiral in arrangement or action.
2. (Crystallog.) Having the planes
arranged spirally, so that they incline all to the right (or left) of
a vertical line; -- said of certain hemihedral forms.
3. (Opt.) Turning the plane of
polarization circularly or spirally to the right or left.