Noun
posek (plural poseks or poskim)
(Judaism) decisor; legal scholar who decides the Halacha in cases where previous authorities are inconclusive or no halakhic precedent exists.
On the other hand, another principle recognizes the responsibility and authority of later authorities, and especially the posek handling a then-current question. Source: Internet
When a rabbinic posek (literally "he who makes a statement", "decisor") proposes an additional interpretation of a law, that interpretation may be considered binding for the posek's questioner or immediate community. Source: Internet
Often, as to the applicability of the law in any given situation, the proviso is to "consult your local rabbi or posek ". Source: Internet