1. Literally, to use a sieve or a similar tool or method to remove small things from a larger substance. Be sure to use a sieve to sift any lumps out of the sugar before you add it to the mixture. People used to sift flecks of gold out of the soil in this river way back in the late 1800s.

2. To isolate and remove something from some larger thing or group after or by careful examination. We have a very rigorous application process to sift unsuitable candidates out of the pool of applicants. The therapy is intended to help patients sift persistent negative or anxious thoughts out of their daily consciousness.