1. To use boiling water to clean or remove something from some material. A noun or pronoun can be used between "boil" and "out." A: "Do you think I'll be able to boil these grass stains out?" B: "Ooh. You might be better off just throwing those pants out, man."
2. To remove or separate something in a liquid by boiling. A noun or pronoun can be used between "boil" and "out." You'll want to boil out the impurities before the water is safe to drink.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.