One possible synonym for the word "quincuncial" is "pentagonal." Both words refer to shapes or arrangements that involve five points or angles. Another possible synonym is "cross-shaped," as "quincuncial" can also refer to a pattern in which four elements are arranged in a square or rectangle, with a fifth element in the center. Other potential synonyms might include "cruciform," "five-pointed," "diamond-shaped," or "star-shaped," depending on the specific context in which the term is being used. Overall, the word "quincuncial" is relatively uncommon and specific, and may not have many truly interchangeable synonyms.