factor of safety

: the ratio of the ultimate strength of a member or piece of material (as in an airplane) to the actual working stress or the maximum permissible stress when in use

Word History

First Known Use

1850, 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!