a five-pointed, star-shaped figure made by extending the sides of a regular pentagon until they meet, used as an occult symbol by the Pythagoreans and later philosophers, by magicians, etc.
pen·ta·cle (pěn'tə-kəl) n. A five-pointed star, often held to have magical or mystical significance, formed by five straight lines connecting the vertices of a pentagon and enclosing another pentagon in the completed figure. Also called pentagram.
[Medieval Latin *pentāculum : Greek penta-, penta- + Latin -culum, diminutive suff.]
"five-pointed star," 1833, from Gk. pentagrammon, properly neut. of adj. pentagrammos "having five lines," from pente "five" + gramma "what is written."