keying by

noun

: the action of clearing an automatic stop in an emergency and permitting a train to pass a signal set at danger

Word History

Etymology

from the gerund of key by, verb

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!