Crossword puzzle clue "spectrum formers"

PRISM, (Greek) a solid figure of which the two ends are similar, equal, and parallel rectilineal figures, and the sides parallelograms

AMEBA, (Greek) a one-celled animal of ever-changing shape, also AMOEBA

AMOEBA, (Greek) a one-celled animal of ever-changing shape, also AMEBA

AMOEBA, (Greek) a one-celled animal of ever-changing shape, also AMEBA

ATOLL, a coral island consisting of a reef surrounding a lagoon

ATOM, the smallest particle in an element which can take part in a chemical reaction

CORAL, a mass of marine animal skeletons

DAM, to build an embankment to retain water