arc of contact

: the portion of a circular surface that is in contact with another surface (as that between a belt and a pulley)

specifically : the arc on a toothed gear between the point where the teeth first make contact with another gear wheel and the point where that contact ends

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!