n A device which separates a suspended, dissolved, or particulate matter from a fluid, solution, or other substance; any device that separates one substance from another.
n electronics | Electronics or software that separates unwanted signals (for example noise) from wanted signals or that attenuates selected frequencies.
n (mathematics|order theory) A non-empty set | empty upper set (of a partially ordered set) which is closed under binary infima (a.k.a. meets).