day degree

noun

: one degree above or below a temperature adopted as a standard (as 42° F for the temperature at which vegetation commences) for a period of 24 hours or its equivalent (as 2° for 12 hours or 4° for 6 hours)

Word History

First Known Use

1884, in the meaning defined above

Love words?

You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Start your free trial today and get unlimited access to America's largest dictionary, with:

• More than 250,000 words that aren't in our free dictionary
• Expanded definitions, etymologies, and usage notes
• Advanced search features
• Ad free!