from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. An apparatus for viewing the sun without injuring the eye.
from the GNU version of the Collaborative International Dictionary of English
- n. A telescope or instrument for viewing the sun without injury to the eyes, as through colored glasses, or with mirrors which reflect but a small portion of light.
from The Century Dictionary and Cyclopedia
- n. A form of telescope fitted for viewing the sun without pain or injury to the eyes, as an instrument made with colored glasses or glasses blackened by smoke, or with mirrors formed simply of surfaces of transparent glass, which reflect but a small proportion of light.
helio- + -scope (Wiktionary)