(1):

(n.) One who sifts flour or meal.

(2):

(n.) An instrument or machine for separating bran from flour, or the coarser part of meal from the finer; a sieve.

(3):

(n.) One who bolts; esp.: (a) A horse which starts suddenly aside. (b) A man who breaks away from his party.

(4):

(n.) A kind of fishing line. See Boulter.