We don't have synonyms for filtre yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are feltre.
(n) :
Obsolete form of filter. [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.]
(v) :
Obsolete form of filter. [(transitive) To sort, sift, or isolate.]
(n) :
Obsolete form of filter. [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.]
(v) :
Obsolete form of filter. [(transitive) To sort, sift, or isolate.]