1.noun(constellation) An unofficial constellation (small group of stars that forms a visible pattern).
"The Big Dipper, Summer Triangle, and Orion's Belt are asterisms."
2.nounA rarely used typographical symbol (⁂, three asterisks arranged in a triangle), used to call attention to a passage or to separate subchapters in a book.
3.nounA star-shaped figure exhibited by some crystals by reflected light (as in a star sapphire) or by transmitted light (as in some mica).