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 from the sugar before you add it to the mixture. People used to sift flecks of gold from 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 with careful examination. We have a very rigorous application process to sift unsuitable candidates from those we would like to have on our team.