Multiply Definition & Meaning - Merriam-Webster
Definition of multiply. (Entry 1 of 3) transitive verb. 1 : to increase in number especially greatly or in multiples
What is the product of 10 multiplied by .5?
Words often have more than one definition. To declare “multiply means to increase” is inaccurate.
That you insist is too bad.
That’s not the mathematical definition, that’s a a literary definition, for example: “be fruitful and multiply”.