Real Dictionary

sift
verb: If you sift a powder such as flour or sand, you put it through a sieve in order to remove large pieces or lumps.
verb: If you sift through something such as evidence, you examine it thoroughly.

sift in American English
to pass through a sieve so as to separate the coarse from the fine particles, or to break up lumps, as of flour
intransitive verb: to sift something
transitive verb: to separate and retain the coarse parts of (flour, ashes, etc.) with a sieve

sift in British English
verb: to sieve (sand, flour, etc) in order to remove the coarser particles