| Webster's Online Dictionary |
| Expressions | Domain | Definition | |
| Herschel double prism | Medicine | A type of rotary prism: a pair of equal power, thin prisms mounted one in front of the other, so that they can be rotated in opposite directions at equal rates to give a resultant power in a single meridian, varying from zero when the apex of one coincides with the base of the other to a maximum when the two apices coincide. Source: European Union. (references) | |
Source: compiled by the editor from various references; see credits. | Top | ||
