The term 'prefix with -hedron' refers to a type of polyhedron, which is a three-dimensional shape with flat faces and straight edges. The crossword solutions provided are TRI (3 letters), PENTA (5 letters), TETRA (5 letters), OCTA (4 letters), DECA (4 letters), HEXA (4 letters), and ICOSA (5 letters). These words all refer to different types of polyhedrons, with the prefixes indicating the number of faces each shape has. TRI is a three-sided polyhedron, PENTA is a five-sided polyhedron, TETRA is a four-sided polyhedron, OCTA is an eight-sided polyhedron, DECA is a ten-sided polyhedron, HEXA is a six-sided polyhedron, and ICOSA is a twenty-sided polyhedron.