Definition of "actinometer" []

• Any of several radiometric instruments, such as a pyrheliometer, used chiefly for meteorological measurements of terrestrial and solar radiation. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Hope with an "actinometer," and obtained results agreeing quite satisfactorily with those derived by Pouillet from experiments made in"
• "In essence the whole shebang had become a giant actinometer."
• "The mystery was not a new type of infernal machine as they imagined but merely a home-made actinometer!"