The phrase "unknown number" refers to a quantity or amount that is not known or cannot be determined. It could also refer to an unidentified person who has not been assigned a specific phone number, hence referred to as having an unknown number.
Sentences with «unknown number»
However, since the pet food scare of 2007 when unknown numbers of pets became seriously ill from contaminated food, pet owners have become more aware of what they feed their furry friends. (dogcare.dailypuppy.com)
Even if you've stopped answering calls from unknown numbers, the ringing can take you out of your flow. (entrepreneur.com)
Every day, many marketing agencies shoot or blast SMS and emails on unknown numbers to promote products & services. (indabaa.com)